I've crossed the Canadian border probably 25x to hunt bear and moose. Never once was I asked for a 4457 form. Not the Canadians and not the US Border guys. I had never even heard of the form until my last return trip. We stopped at the US border to check in a bear that my buddy took. An overly aggressive US agent decided to have a little fun with us for no particular reason because, other than the absence of the 4457 form, everything was in order. As LEOs ourselves, we were all respectful and professional.
The agent insisted that we were always required to have a valid 4457 form to reenter the US with firearms. That's technically untrue, it's just a tax avoidance form. He said how does he know the rifles weren't stolen, even though we produced the Canadian firearm forms indicating that we brought them over 7 days earlier. They emptied our SUV and had 3 of us remain in a room like a bunch of wall hoppers. No cell phone use, no bathrooms, no nothing. It took them over an hour to verify that the firearms weren't stolen. Then they had us fill out new 4457 forms which made little sense since we were already back in the US. And while the agent suggested that he could refuse us entry into the US, my attorney claimed that agents are without authority to keep US citizens out of the US. We all had passports even though they weren't required to drive to Canada and back.
Moral of this story - make SURE that you have all of your paperwork in order. Dot the Is and cross the Ts. You just never know who you'll run into at the border.
