There are a fair number of legal issues related to music. Examples are downloading copyrighted songs and performing music you obtained "unofficially".
Should questions about legal issues be allowed?
I think these questions should be off-topic.
Questions about legal issues are either too localized (asking about laws in a specific area) or too broad (we can't answer well without knowing your specific area), and rely on legal expertise and not musical expertise. Most of these issues are only tangentially related to music; downloading a book illegally or reading it aloud in public have largely the same implications as the issues mentioned above in the question.
While answering these questions could be helpful to musicians, I don't think they are questions about musical practice, performance, theory, or history (the scope of the site). The scope should not be expanded to include them because we are music experts / enthusiasts, not legal experts. There may also be legal ramifications of giving advice on legal issues, which we don't want to deal with.
I've made a more expansive post on this subject for Gaming, which I think largely applies here as well.