If the abuser has been convicted of a domestic violence misdemeanor or felony, can s/he legally keep or buy a gun?
No. Under federal law, if the abuser has been convicted of any felony or a domestic violence misdemeanor, s/he can never legally have or buy a gun.* Please talk to a lawyer who is knowledgeable about federal gun laws to find out if the abuser's gun can be taken away based on your specific situation.
* 18 USC §922(g)(1),(9)