"People will smuggle illegal guns from abroad. Or buy the parts and assemble them. Or get a machine shop and make them."
A regulation, no matter its aim, does not require 100% compliance to be an effective deterrent. I'm not saying this plan will work, but a generic "people will get around it" argument is not illuminating.
Well, kinda, but not to same degree. Wired money is obviously way easier to smuggle than physical goods...
In this thread someone said it's like trying to stop the import of illegal drugs. Regulations seem to work for Singapore.
https://en.wikipedia.org/wiki/List_of_countries_by_prevalenc...
Deterring what? "Illegal immigration" or "people walking across the border"? If it is the former, then that plan is just so stupid to be of any value. Banning transfer of money from US to Mexico to make Mexico pay for "building a 10 ft high border-wall" is ... wow, just saying that out loud feels weird.
(PS: I'm neither an American nor a Mexican!)
I'm not making a judgment here, just trying to clarify the worldview.