I have a three part approach to solving the issue:
Change the numbering system to create blocks of numbers that are specially set aside for various legal robocalling entities, 911 call back, banks, etc.
The Telecommunications companies and the companies that issue caller id's should be obligated to weed out potential illegal robocalling enterprises by either not issuing them a number from the designated block, not issuing them the caller id that they request, and by reporting these companies to the FTC. The offending agencies would incur stiff penalties for violation and non-compliance.
The final part is updating the Privacy managers to insure that they are able to block/allow specific international area codes along with blocking/allowing domestic area codes and the new block prefixes.
Image courtesy of http://www.pibblesnme.com/2012/08/quit-calling-me/. downloaded 1-15-2013 2:20am