There is the do not call list. If you tell not to call and they call again, in theory they have to pay a fine. The real problem is with ip phones, the calling endpoints can be changed very easily. Any one can register a local number within a minute and make calls. An overseas company (scammers or legit), can call and the odds of any action taken against them is nill. With the ease of them changing numbers or buying a whole bunch of different numbers, blocking them does work well.
To quote Ronald Reagan: “The most terrifying words in the English language are: I'm from the government and I'm here to help.”
I've been on the "do not call list" for years and I still get unsolicited spam and robo calls.
My understanding is that the fines against spammers are mostly ineffective and the government has been unwilling to place heavy CRIMINAL penalties on the spammers, i.e., putting them in prison would be a stronger deterrent than fines. Also, much of the spamming originates off-shore. We need laws that allow us to extradite spammers located in foreign nations for criminal trial here.