Award tickets for someone else, then getting paid back in miles

I've been redeeming miles for a friend because he doesn't have access to the award tickets that I do (premier gold). He's then been transferring miles from his Chase rewards account to pay me back.

Does that violate UAs program rules? It's not necessarily bartering or sale, but it may be something that UA objects to.

Any advice? My biggest concern is losing status and/or them revoking his tickets.

Thanks