I have completed EMT training earlier this year, but I don't work as an EMT. My training was just outside of Seattle. One of my instructors is a Seattle police officer and he was very insistent that we never treat anyone if they have a gun on them, or a knife, no matter how calm and respectable they seemed. He said to always make it a point to look for the clip of a knife. Though EMT's have a legal obligation to treat you, it does not apply to them putting themselves into danger. Being a gun owner myself, I would probably treat as long as they were not aggressive or in a state of altered awareness. If you are in a car accident and are taken to the hospital in an ambulance, you will wind up with all your clothes cut off of you, even if you are uninjured if there is a significant mechanism of injury. You'll lose the gun eventually, so I don't think it's such a big deal to let the police take them, unless you crashed because they were chasing you.