Look at last year's mass shooting in Buffalo, where a racist drove halfway across the state to shoot up a grocery store in a black neighborhood. He shot 12 people, including a "good guy with a gun" that the NRA claims stops attacks like that.

He had bought his rifle legally in NYS, but went across the border to PA to buy 30 round magazines, which are illegal in NY.

Having access to 20 more rounds per mag than NY's max certainly didn't help things, but that terrorist attack would probably still have happened if NYs laws were nation wide.

The problem is both that location-specific gun control is ineffective because you can just go a state/city over, and that passing effective gun control even in a state like NY is almost impossible.