As long as it's not cranked on tight as all ####, you can get a slim butter knife in alongside the trigger guard and depress the spring loaded toothed bit that holds both halves together. (I'm assuming the Masterlock ones or similar here) The simplest one I've removed though involved yanking two screws and removing the trigger guard . That's the easiest route if you're lucky enough to have it on a gun assembled in that fashion.....