Did the person in question get notified in writing that they had forfitted there gun right.In theory ,although I understand government communication is not always accurate but if one looses there gun right they supposed to be notified.

Example if one is convicted of a felony or domestic violence ,the judge should say at sentence or plea bargain that gun rights have been forfitted.And that also should be indicated in post conviction paperwork that every convict is given by right.

Unless there was a communication failure (which happens) your friend aught to already know if there gun rights have been forfitted.