<p>Nice question.</p>
<p>Problem is we often befuddle between what is <em>illegal</em> and what is <em>unethical</em> (see this <a href="https://skeptics.meta.stackexchange.com/a/4624">discussion</a>).</p>
<p>One thing is clear though: we need proper, clear citation to any work/pre-print/literature. Those should be coupled with DOI, arXiv identifier or whichever applies to the work concerned. These would ensure once a link dies/rots, future users can still seek the required paper.</p>
<p>Coming to the bone of contention: should we cite Sci-hub/lib-gen or other such repositories?</p>
<p>See, it's an open secret that many people around the world (especially South-Asian countries) use these resources and at least it would not be too much to say that even more people are getting or already are acquainted with such resources. So, if they <em>need</em>, they would <em>resort</em> to such resources, irrespective of whether one explicitly includes such links. Personally, while I admit even I use Sci-hub, I never cite them. While I cannot forbid others, I think it's apt to not engage in such practice of using resources likes Sci-hub in our posts here.</p>
<p>Why? Because it can be political and there can be uncharted legal issues not explored/beyond our knowledge:</p>
<blockquote>
<p>... a link to Sci-Hub is, itself, a radical expression of personal politics. In keeping with our desire to minimise the expression of party/personal politics here, I would therefore recommend avoiding such links.</p>
</blockquote>
<p>Pertaining to legal issues, one can check these related posts and links therein:</p>
<p><a href="https://meta.stackexchange.com/questions/114919/what-should-i-do-when-i-see-copyright-violations-posted-on-stack-overflow">What should I do when I see copyright violations posted on Stack Overflow?</a> (SO)</p>
<p><a href="https://meta.mathoverflow.net/questions/3953/what-to-do-when-a-post-contains-a-suspicious-link-possibly-with-copyrighted-m">What to do when a post contains a &quot;suspicious&quot; link (possibly with copyrighted material)?</a> (MO)</p>
