Part 1: on subjective stack exchange sites, you can and should "close" answers.
I could explain this myself, but shog does a better job of this (https://worldbuilding.meta.stackexchange.com/questions/5168/can-post-notices-on-the-hard-science-tag-actually-do-something/5170#5170), so I'll let him explain:
This is one of those areas where a topic breaks the model a bit.
For questions, we have essentially two axes for voting: Useful vs useless (voting), appropriate vs inappropriate (closing).
Closing a question - possible even if highly upvoted - makes it eligible for deletion and prevents answers from being posted, providing strong encouragement for improvement.
For answers though, there's only one axis: useful / useless. An answer with a positive score can't be deleted except through moderator intervention, and there's no equivalent to blocking answers for an answer; years ago we tried using Community Wiki as a "reputation denial" feature but this failed miserably - the closest thing we have today is probably locking, which prevents voting but also prevents both improvement and deletion.
The solution we arrived at on Stack Overflow was to simply discourage questions whose answers cannot be effectively moderated based on the single useful/useless axis. This solved the immediate problem*, but did so by pushing it off onto other sites: Software Engineering, The Workplace, Software Recommendations all allow or have allowed questions for which answers may be difficult to evaluate on a single axis and thus require manual intervention by a moderator in order to remove those that violate community norms.
One reason to close an answer is because it's off-topic.
I think you've made a great case in your question for requiring that answers be on topic, ie that answers answer the question rather than go on needless tangents about legal issues. If I ask a question on this site, it's because I need help with interpersonal skills, not legal advice.
Of course, there are a lot of gray areas: maybe an answer spends a dew sentences on legal advice but then also talks about interpersonal skills. In this case, edit out the legal advice and see if the answer still makes sense. If it doesn't, then the answer isn't about interpersonal skills and should be "closed" as off topic.
until SE gives us community tools similar to close votes but for answers, it's the job of the moderators to "close" problematic answers.
The only tools that are equipped for this problem-- deletion of positively scored questions and post notices--are moderator only. So moderators: get a consensus and start using these tools. And since nobody reads meta, the best way to start building a consensus is by downvoting and leaving comments on the offending posts.
