You may or may not be legally obligated (although this obligation is not realistically enforceable by law); as for morally obligated, it depends upon the nature of the act. There is imperfect overlap between things defended by law and by morality. If we're talking piracy or jaywalking or buying modafinil on the black market, you may be overexerting your civic powers here, and your conscience can relax. If the matter at hand involves violence, and you can expect to save some people through your report, then maybe it's better to get involved. For all matters in-between, both approaches may be valid in certain proportions, so apply common sense.
It was a misunderstanding, but for the record, what I thought was going on was far worse than buying modafinil, or any other illicit substance, and sort of indirectly involves violence.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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