I spotted these two articles recently that struck me as useful resources for writers. Quite a few states restrict the ability to own guns of those convicted of domestic abuse, charged but not yet tried, or subject to a protective order. (I’ve written about protective orders in domestic abuse cases here and here.)
This article chronicles recent changes in state laws, as well as changes under discussion.
And here’s a Q&A on the topic.
And here’s a pair of directories to gun laws, one state by state and one by policy. (I’ve not yet used it, and can’t vouch for its accuracy; if a state law is key to your story, check the statutes.)