Willie nailed it - for all intents and purposes the guns belong to you. There is no such thing as loaning a firearm. As the old saying goes "possession is 9/10 of the law" In this case it's 10/10
To transfer them back to someone you know to be a convicted felon with a history of substance abuse would not only be irresponsible, but a felony itself.
I would only contact his PO should the issue be pressed further.
"The best diplomat I know is a fully charged phaser bank" - Montgomery Scott