Third party doctrine for one: the data held by third parties has no expectation of privacy, even if it's about you.

From Wikipedia:

The third-party doctrine is a United States legal doctrine that holds that people who voluntarily give information to third parties—such as banks, phone companies, internet service providers (ISPs), and e-mail servers—have "no reasonable expectation of privacy" in that information. A lack of privacy protection allows the United States government to obtain information from third parties without a legal warrant and without otherwise complying with the Fourth Amendment prohibition against search and seizure without probable cause and a judicial search warrant.

Basically the government's argument: if you wanted it to remain private, you wouldn't have given it to someone else.

I'm reality, it's an area of law that desperately needs to be updated.

It will take someone being brought in on evidence gathered by this method to get it overturned. It would probably wind its way up to the Supreme Court.

PATRIOT