In my estimation blocking robocalls is only half of the problem. The other part is the ability to spoof caller ID. While there is an occasional legitimate reason to do this, it is being abused far greater than it should be.
I would suggest that anyone with a legitimate need to show caller ID that does not point back to the calling number would need to register the spoofed information with their telephone service provider. All other calls with incorrect caller ID should be blocked right at the source, or when they come into this country.
I am on the "Do Not Call" list (which I think provides a list of good numbers for the telemarketing industry), but how can I complain about calls received when they came from the little old lady down the street, or many that show "not assigned"?