Enough minor inconveniences and the barrier to entry will go up, this will favor the larger players but those you can then go after with other means. It's never going to be a one-stop solution.

Ideally there would be a warning that a call does not originate locally, routing the call through a local representative would generate yet another signal that you might be able to close off, including the possibility to declare the possession or hosting of certain gear illegal. You'd have to maybe do some pattern matching to spot problematic numbers and/or have a place to report them easily.

If the will was really there I'm pretty sure this problem could be tackled.