Here is a user linking to apparently illegal material:

TCS online library

How should we deal with this issue?


  1. I think we can restrict the discussion to unauthorized online copies of copyrighted books. (If you have other similar things in mind please comment so we can add it to the list but for now this seems to be sufficient since we haven't had any other related case AFAIK).

  2. My intention for asking this question was not about legal issues (as I have stated in my answer below) but how we should deal with these (links to unauthorized online copies of copyrighted books). Do we need a policy? If yes, what should be the policy?

Update (Jan. 19, 2011):

I have posted a draft policy here.


This discussion got a bit sidetracked by the legal issues.

I think we should be polite, respectful, and professional. Certainly we shouldn't take part in any dubious activity that might harm the feelings of our colleagues.

I don't want to be associated with a site that distributes links to files that are copied without the permission of the author or the copyright holders.

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    $\begingroup$ I find it unfair to say that the discussion got “sidetracked” by the legal issues. $\endgroup$ – Tsuyoshi Ito Jan 18 '11 at 13:40

Edit: It seems that my previous answer was not clear enough.

It seems to me that you and several other people are using the word “illegal” as a synonym to “bad.” Although many people confuse good/bad with legal/illegal, it is better to distinguish these two distinct notions.

I do not think that we should expect that moderators know legality or that moderators should base their decisions on whether the material is legal or not.

I do not like a free online copy of a book (or a link to it) when it is not authorized by the authors, no matter whether it is legal or not. I do not know exactly why I do not like it, but it is not because it is illegal (in some places). I somehow feel that such a copy is disrespectful to the authors.

However, moderators should not act based on personal preferences. If we want moderators to act on cases like this, we may have to make a policy but I am not sure if it is possible.

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    $\begingroup$ this is what I was referring to when I said "obvious".. $\endgroup$ – Jeff Atwood Jan 16 '11 at 7:47
  • $\begingroup$ I rewrote the answer almost completely because it seems that my previous answer was not clear enough. $\endgroup$ – Tsuyoshi Ito Jan 16 '11 at 23:12
  • $\begingroup$ Thanks Tsuyoshi. I am not using illegal as a synonym for bad. I really don't think that anyone participating in this discussion thinks that the stuff linked to by OP in the post I have linked to is illegal not just under US laws which I think are the laws that apply to the site but also international copyright laws. So it is pretty clear that the books on the site is illegal. I don't know what I could have used in place of the word illegal. Maybe unauthorized copyrighted material would be more specific. $\endgroup$ – Kaveh Jan 17 '11 at 6:31
  • $\begingroup$ I have tried to explain in my answer that the issue is not being illegal or not, it is also not about being good or bad (at least not that simply), the question is about how should we deal with them: 1. should we have a policy about them? 2. should we a)allow b)allow but discourage 3)disallow them? ... $\endgroup$ – Kaveh Jan 17 '11 at 6:31
  • $\begingroup$ @Kaveh: You wrote “Should we permit linking to illegal stuff?” in the first place, and I replied that whether something is illegal or not cannot be a good criterion to decide moderator’s action. Now your ask how we should deal with “them,” but I really do not know what “they” refer to. $\endgroup$ – Tsuyoshi Ito Jan 17 '11 at 21:55
  • $\begingroup$ I got it. I think we can restrict the discussion to unauthorized copies of books. I will edit the question. $\endgroup$ – Kaveh Jan 18 '11 at 4:14
  • $\begingroup$ @Yaroslav: I do not know to whom your comment is directed. At least I am fully aware of the difference between “unauthorized” and “illegal”; otherwise I would not have written this answer in the first place. $\endgroup$ – Tsuyoshi Ito Jan 18 '11 at 23:20
  • $\begingroup$ @Yaroslav: Why are you writing your opinion as comments to my answer? I cannot see any relevance of your comments to my answer. $\endgroup$ – Tsuyoshi Ito Jan 19 '11 at 0:36
  • $\begingroup$ Authorization can be made on behalf of the author by author's heirs, owners of publishing rights or the government. When rights to a book are resold, authorization rights get transfered, so authors don't explicitly authorize new copies. Bottom line is that you can't treat the issue of authorization separate from the legal issue. $\endgroup$ – Yaroslav Bulatov Jan 19 '11 at 20:15
  • $\begingroup$ @Yaroslav: Ah, I see. That is a good point. If authorization cannot be separated from legality, we cannot use authorization as a criterion either. $\endgroup$ – Tsuyoshi Ito Jan 19 '11 at 22:07

Linking to egregiously illegal content should not be allowed.

If it is a "grey area" then, depending on the intentions of the poster, it can be OK. But if it is clearly illegal, then no.

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    $\begingroup$ but that requires legal determinations on our part, something that I certainly am not competent to do. $\endgroup$ – Suresh Venkat Jan 15 '11 at 6:40
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    $\begingroup$ @suresh so you abdicate any responsibility at all? I think EGREGIOUSLY illegal is a pretty clear guideline. For example, linking to PDF copies of copyrighted, commercially available books, which has happened on Stack Overflow before. We remove such links as a matter of policy. Why would you feel "incompetent" to make such a decision? $\endgroup$ – Jeff Atwood Jan 15 '11 at 6:45
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    $\begingroup$ well in this particular case, the site is hosted in Russia. I am certainly not 100% sure about how copyright law is transmitted across borders. Secondly, at least with other media content (videos/music etc), the injured party files a claim under the DMCA, does it not ? In any case, this is precisely my point: there's law here, and I'm not a lawyer to interpret the law correctly. $\endgroup$ – Suresh Venkat Jan 15 '11 at 6:56
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    $\begingroup$ The problem with this answer is that nothing is obvious, at least to me, when legal issues are concerned. $\endgroup$ – Tsuyoshi Ito Jan 16 '11 at 7:38
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    $\begingroup$ @Jeff: It seems a very dangerous game to require moderators to try to make judgements as to what is legal and what is not. My guess is that it will make people reluctant to take up the role if they risk any liability for failing to remove illegal content (and I doubt anyone on this site knows enough about the law in any jurisdiction to catch all violations). It would seem a much better solution to remove content for violating certain specific tenets of the site rather than requiring moderators to make a determination about the legality. $\endgroup$ – Joe Fitzsimons Jan 16 '11 at 8:21
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    $\begingroup$ I must agree with Jeff here. The linked website is egregiously illegal. Most of the books on that site are in print and cost money to buy. Furthermore, almost all of those books have a line which reads something like this "no part of this book may be transmitted in any form or by any electronic means, mechanical, photocopying, recording, or other without written permission from its author." $\endgroup$ – Robin Kothari Jan 16 '11 at 21:01
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    $\begingroup$ @Jeff: I disagree. A significant fraction of author-posted online preprints directly violate the transfer of copyright contract signed by the authors, and are therefore illegal. The theoretical computer science community ignores, even encourages, this obviously illegal behavior, because we don't find it unethical. The linked Russian site is posting complete electronic copies of books, in violation of the authors' express wishes. The community should not encourage such unethical behavior; links to egregiously unethical content should be deleted. $\endgroup$ – Jeffε Jan 17 '11 at 17:09
  • $\begingroup$ @jeffe that's fine, I see that as mostly semantics, but whatever achieves the desired result is fine by me $\endgroup$ – Jeff Atwood Jan 17 '11 at 21:39

If a link seems suspicious to you, the poster should deliver sufficient (i.e. convincing our moderators) proof that the link is legal. This can, for instance, be achieved by referring to a suited license or a public download on the autor's site. If such proof can not be delivered, the link should be deleted to avoid further hassle.

We could advise users to provide instructions how to find the document instead. Given correct search terms for, say, Google, I have seen this done nicely.


I agree with the most of what is said in other answer. I am not a lawyer and what I am not sure if what I write below is correct (it would be nice if people from SE ask their lawyers to verify/clarify them for us). Also it would be nice to know the policy on similar sites like Wikipedia.

Now I think we should separate the issues:

  1. The first thing is which law? I think the answer is the law of the state/country that the servers for SE are placed. That is the law that applies to the site and having an international community does not change it. The site is responsible under that law, not say Russian law.

  2. The second issue is who is responsible against law if something bad happens. I think the person who has committed the illegal activity is responsible, I don't think the community or the moderators are responsible, and if something goes wrong that is the problem of people in SE (the community and the moderators are helping the SE people, but obviously the owner of the site is SE and we are not responsible if someone else does something wrong). (I am not sure what will happen when ACM becomes involved, but my guess is that they would not like to have any kind of legal responsibility about such matters.) So I don't think we (community/moderators) have a duty to remove illegal stuff.

  3. The third issue is do the responsible people for the site have a duty and legal obligation to remove the illegal stuff in general? Again, I don't think so. We and they are not lawyers and cannot make the decisions about what is legal and what is illegal. I am guessing this based on the discussion on MO. The situation is obviously different if there is a court order and/or they are obliged to remove some stuff under some law (say DCMA).

  4. The forth issue which was my intention when I asked this question is about our own policy, not about legal obligations/duties. Should we allow things like links to copyrighted books where it seems that they are not legal? This is not about law, this is about what we think and what policy should we have, and the decisions are of course will be somewhat subjective as other decisions we make about closing or deleting posts. So the main question is "Do we (i.e. the cstheory community) think it is OK and suitable to have such links on a professional site?" I don't know. I personally don't like the current copyright laws, but is it OK in our opinion to allow links to unauthorized online copies of books written by our colleagues? The people on MO seem to be OK with this unless there is a complaint (say from the author). The people on SO seem to have a different opinion. The other issue is the consequences of a decision. What will be the effect of allowing them on questions/answers/community? What will be the effect of discouraging them? What will be the effect of disallowing them? Should a question asking for an illegal online copy of a copyrighted book permitted? Or such links in answers to a CW question about online books? ...

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    $\begingroup$ I actually like the MO discussions on this, and am closer to their way of thinking. $\endgroup$ – Suresh Venkat Jan 16 '11 at 21:38
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    $\begingroup$ I feel that a considerable part of researchers would not be happy to see such links on a professional site. I am also concerned a little bit about the effects of allowing such materials and the possibility of the site becoming a hub for such links (though it seems that this has not happened on MO). I think I am closer to allowing them to a limited extent (e.g. question asking for such link should be closed) but also discouraging users from posting such materials in general by down-voting and comments like posting such links is not a nice practice. $\endgroup$ – Kaveh Jan 17 '11 at 6:47
  • $\begingroup$ Kaveh: maybe it's time to draft a policy :). I like these two points you made, and also maybe we should have some text about violating author intent (that JeffE mentions in regard to this particular site). $\endgroup$ – Suresh Venkat Jan 19 '11 at 3:50
  • $\begingroup$ @Suresh, I personally still don't know which policy I would support, but I can draft a policy. I will post a new question so others can also post their drafts and then we can vote. $\endgroup$ – Kaveh Jan 19 '11 at 5:19
  • $\begingroup$ @Suresh, I have posted a draft. $\endgroup$ – Kaveh Jan 19 '11 at 5:58
  • $\begingroup$ As for the legal part: US law can probably not be applied to a person from elsewhere. So either users are to be hold by the law of their home country (practically impossible) or we have to assume the site owner is liable and assume US law. I do not know about US law, but in Germany site owners are liable if users post illegal material. If this is the same in the US, it immediately renders your current suggestion dangerous since a linked copy that is authorised but illegal (i.e. author gives you a permission he legally can not give) can still cause problems for the site owner. $\endgroup$ – Raphael Jan 19 '11 at 10:31
  • $\begingroup$ Also, it is not clear to me wether, by your policy proposal, the poster has the obligation to prove authorisation or legality in order to have his link allowed, or moderation has to prove the source is unauthorized and illegal in order to be allowed to delete it. This question should, of course, only arise when the source is in doubt, but is of essence then. $\endgroup$ – Raphael Jan 19 '11 at 10:33
  • $\begingroup$ @Raphael: It does not matter if it applies to the persons, it applies to the site and what is on it. We are not making legal judgments here. In any case I am not a lawyer and I think we should leave this issue to the SE people and their lawyers, I think I made clear that this is not about legal issues, it is about our own internal policy and that is all. As JeffE has stated above many authors make the final versions of their papers on their sites even when it is illegal under copyright. Final words: lets leave these issues to the people in SE and their lawyers. $\endgroup$ – Kaveh Jan 19 '11 at 13:46
  • $\begingroup$ No one needs to prove anything by default, I personally think that the cases where a user posts such a link and claims it is a legal copy will be very infrequent. $\endgroup$ – Kaveh Jan 19 '11 at 13:47
  • $\begingroup$ part of a recent relevant email from SE: "[...] you are not employees of Stack Exchange. [...] If you are ever notified about copyrighted material, and feel like taking it down, that's cool... but you are not required to do so. You are not DMCA agents (we have those of our own). If you get a request for takedown, you can either remove the post OR point the person to the Copyright Policy linked below." $\endgroup$ – Kaveh Apr 15 '12 at 23:26
  • $\begingroup$ "Here at Stack Exchange central, we have to be concerned about claims of copyright infringement that may not be valid. If WE (Stack Exchange Inc.) get notices to take down offending content, the claimants need to follow DMCA procedure and contact us with the correct form. It's all outlined in the Terms Of Service "Reporting Copyright Infringements" Our TOS covers all the relevant info about DMCA.The claimants will have to contact us with the necessary forms and information. That makes the issue pretty simple and straightforward on your end. Delete or reply with link." $\endgroup$ – Kaveh Apr 15 '12 at 23:27

I think it's perfectly reasonable to delete posts, and even warn/ban users for violating US law. Even if you don't agree with current laws, the notion that StackOverflow is somehow going to be able to absolve itself of responsibility for copyright infringement seems naive to me.

The StackOverflow and StackExchange sites are already a pretty big deal, at least in my estimation. I'm not a lawyer, but I know enough to feel comfortable saying if site policy does not include a strict ban on copyright infringements, you're basically begging for a lawsuit once you get to be a big enough deal as a company.

The question is: Will anyone care enough to sue if you don't include an explicit policy banning illegal activity? If all that's being posted is links to math textbooks, it's unlikely that the company that SO will get hit with a lawsuit. But if (for example) someday someone starts "music.stackexchange.com", and it becomes a safe haven for copyright infringement that hurts the bottom line of someone who cares, I would bet real and significant amounts of money that lawyers for some company somewhere will come after you.

So, the short version of what I'm saying is: Don't ban illegal activity at your own risk. And by "your own" I mean "StackOverflow's." Just saying.

  • $\begingroup$ I think they can ask users not to post such content in the FAQ, but I think it will be similar to Youtube and Wikipedia. Someone asks them to take these down and they do. What will happen if some users posts such material? Do they need to go and take them down even when no one has asked for such a thing? I am not a lawyer but my guess is that they don't need to and in fact it will be a difficult thing to do in practice. MO have allowed such links and based on the discussion on their meta it seems that they have not had any problems till now. $\endgroup$ – Kaveh Jan 19 '11 at 14:00
  • $\begingroup$ They can add also a spam-like flag option. $\endgroup$ – Kaveh Jan 19 '11 at 14:01

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