Just for fun scenario

[Mortblanc]

No one said a thing about it being your local, friendly, understaffed, whiny British natives doing the application and enforcement of these restrictions.

I assure you that there are groups that can enforce ML on a population of 60 million efficiently and without hesitation. The Soviet Union maintained almost these exact regulations on a much larger population for more than 50 years. You still need "travel papers" in many areas.

Just pretend Churchill is dead and there is no inspiration for stopping the next invading army from spilling onto your shores.