The Telecommunications Act of 1992 established a number of consumer protections, most notably, those on "slamming". It also established that telemarketers had a right to call but consumers had a right to have their name/number put on a do not call list.
Although a few telemarketers did go to the time and expense of estabishing, maintaining and honoring such a list, the law was essentially ignored by the industry. The industry was also arrogant in their refusal.
They had 11 years to conform. So when you hear the telemarketing companies talk about the economic dislocation that the the list will cause remember that they had 11 years to gradually change.
99% of telemarketers are outlaws.
Two wrongs still do not make a right.
Hank