Legal Advice is Off-Topic
Legal advice is off-topic almost everywhere on the SE network. The lone exception at the present time is http://area51.stackexchange.com/proposals/67858/law.
Essentially, legal questions rarely have canonical answers, and invite opinions and interpretation. Even when the question is peripherally on-topic, such questions almost always end up as "broken windows" on a site. Curation is essential to a healthy site; for example, even a well-written post on bee-keeping doesn't deserve to remain on Project Management Stack Exchange just because it's well-written or valuable in some abstract sense. If it's off-topic, our duty to curate the site requires that we take the appropriate actions.
If there's a valid migration target, the content can be moved. Otherwise, it ought to be closed and/or deleted.
Use Community Wiki to Salvage On-Topic Content
In my opinion, the correct thing to do is close the question, and then eventually delete it as off-topic. If you feel there is value in the content of answers and comments, then you could rework the question (with appropriate links and citations) as a PM-related community wiki post, and place the relevant content that you deem worth salvaging into a community-wiki answer.
The important thing is that the content needs to be:
- Refactored to be on-topic within the site's guidelines.
- Properly cited and linked (even if it's to a closed/deleted thread) to comply with the CC-BY-SA 3.0 license.
Alternative: Re-Homing Content
If it can't be salvaged in that way, then you are free to reuse the content in accordance with the licensing terms. You could post the content on a personal blog, other wiki, or anywhere else the content would be on-topic and in compliance with the license.
If the current content can't be reworked into a valid PM question, then you should seriously consider migrating any valuable content to an alternative location. Whether or not it's worth your effort to do so is of course a personal decision. YMMV.