I asked this this question. It was put on hold by Bart van Ingen Schenau, who kindly and patiently explained that he rejected the question because of a community consensus that programmers cannot authoritatively answer questions involving the legal topic at hand (copyright law).
I have searched Programmers Meta, and I find no evidence of such a consensus. To the contrary, I find a pronounced lack of consensus. Relevant posts seem to be What types of legal questions are on-topic here?, Are software law questions off-topic here?, and “consult your lawyer” answers. Among those discussions, there seems to be a contingent arguing that programmers are qualified to answer no legal questions; a contingent arguing that programmers can answer only those legal questions intimately related to programming; a contingent arguing that programmers can answer a wide range of legal topics as long as "common sense" is applied to the interpretation of the answers; and a contingent arguing that programmers may potentially be able to answer any legal question. No contingent clearly dominates the others.
As a newcomer browsing the documented record, my perception is that the community is very far from a consensus on this matter. Nevertheless, community consensus was cited in Mr. Schenau's explanation for the rejection of my question. The apparent implication is that a non-existent community standard is being used to justify the rejection of questions on Programmers Stack Exchange.
I come to Meta (at Mr. Schenau's suggestion) in search of clarity. Does there exist a consensus on programmers' inability to answer questions on copyright law sufficient to justify the rejection of questions on that topic?
My question is attracting answers which are not quite on-point, so I think it would help if I elaborate.
I believe the help center guidelines are out-of-sync with community standards, especially when it comes to deciding whether or not legal questions are off-topic. I suspect what has happened is that the community has formed a shared opinion over time, but hasn't kept the guidelines up-to-date. That's okay -- We can fix it by establishing what the community standards are, then updating the guidelines to reflect them.
Let's start with the one question where I've been told there is a consensus: Does everyone agree that programmers cannot authoritatively answer questions of copyright law? If yes, then let's edit the guidelines to say that copyright questions are off-topic for that reason. If no, then let's tell people to stop citing that as a reason for closing questions.
It seems likely that follow-up questions will be necessary. Doc Brown says we shouldn't encourage legal advice because it may be illegal to do so, or carry too much responsibility. Maybe we should look for a consensus on that point and, if we find one, write that into the guidelines. Telastyn suggests that copyright questions are too specific to be useful. Perhaps the community agrees with that, and it should be written into the guidelines. Snowman suggests that legal answers carry too big a risk of leading to bad decisions. Etc. Etc.
But let's take things one step at a time. The question on the table is whether or not we agree that programmers are incapable of giving authoritative answers to copyright questions. Yes or no?
Thanks to everyone who answered or commented on this question. Here is a summary of what I learned:
1) Some respondents suggest that my question is based on a misconception. I had believed that Programmers Stack Exchange first establishes a consensus on which topics should be allowed, then writes those criteria into the help center guidelines, then instructs its moderators to close only those questions which fail to meet the guidelines. (Let's call this System A.) However, Eric King, Walter Mitty, and Rob Y suggest that Programmers Stack Exchange doesn't work this way. Instead, moderators vote to close and reopen questions at their own discretion, and the balance of votes, not the help center guidelines, determines what is on-topic or off-topic. Consensus doesn't play a formal role in the process, but you can infer consensus by looking at which questions remain closed and which remain open. (Let's call this System B.) I felt this was too big a concept to address properly in the comments here, so I started a new question to discuss it. Thank you to Eric, Walter, and Rob for opening my eyes to System B. It explains a lot of what I see on PSE, and it helps me to understand the replies to my question. If Stack Exchange does, in fact, work along the lines of System B, then my original question and my earlier edit in which I suggest that we bring the help center guidelines up-to-date with community standards are misguided; the site simply doesn't work the way I expected.
2) Some respondents assert that the help center guidelines prohibit most legal questions through their prohibition on legal assistance. Snowman says that anything which crosses the line beyond "how the license works" is "explicitly off-topic per the help center". MichaelT says "The help center already has 'legal advice' in there as off topic" and suggests that this implicitly extends to "interpretations". Robert Harvey says "Legal interpretation, advice, and assistance are all the same thing." My conclusion is that some moderators believe the help center contains a broad prohibition on legal questions, and may use it to justify the closure of any question with a legal aspect.
3) Several respondents went beyond answering whether or not there is a consensus on whether programmers can authoritatively answer questions of copyright law, and tried to explain why programmers cannot or should not answer legal questions in general. The diversity of these replies convinces me that there is no doctrine on the subject, but rather a bunch of individual theories.