There was a rumor years ago in these parts of a deputy who carried his revolver with a trigger lock installed. He was not well regarded.
I attended FITP with an investigator from IRS OIG. Their policy was to put a trigger guard lock on the pistol after removal from the holster...without manipulating (unloading) the weapon. They apparently had a few bed pops in hotel rooms or something. I don't know if that policy is still in effect.