Doesn't track for many places in the US. Chicago has some of the strictest gun control in the country, yet also has a mass shooting every other week in the summer.
In other words, it should be obvious that regulations in one city do not hamper interstate trade - or heck, they likely don't hamper intrastate trade either, but I don't have any examples in my head about that specifically.
Also while impossible to prove, I think the numbers would be even higher in the city without the control in place.
Gary, Indiana shares a fence with Chicago: The fence sits on the Indiana/Illinois state line. Indiana has fairly lax gun laws. Also of note: There are not border checks on that line, nor on the border of Chicago.