https://theintercept.com/2017/03/13/rand-paul-is-right-nsa-routinely-monitors-americans-communications-without-warrants/

ON SUNDAY'S Face the Nation, Sen. Rand Paul was asked about President Trump's accusation that President Obama ordered the NSA to wiretap his calls. The Kentucky Senator expressed skepticism about the mechanics of Trump's specific charge, saying: "I doubt that Trump was a target directly of any kind of eavesdropping." But he then made a broader and more crucial point about how the U.S. Government spies on Americans' communications – a point that is deliberately obscured and concealed by U.S. government defenders.

Paul explained how the NSA routinely and deliberately spies on Americans' communications – listens to their calls and reads their emails â€“ without a judicial warrant of any kind:

The way it works is, the FISA court, through Section 702, wiretaps foreigners and then [NSA] listens to Americans. It is a backdoor search of Americans. And because they have so much data, they can tap — type Donald Trump into their vast resources of people they are tapping overseas, and they get all of his phone calls.

And so they did this to President Obama. They — 1,227 times eavesdrops on President Obama's phone calls. Then they mask him. But here is the problem. And General Hayden said this the other day. He said even low-level employees can unmask the caller. That is probably what happened to Flynn.

They are not targeting Americans. They are targeting foreigners. But they are doing it purposefully to get to Americans.

Paul's explanation is absolutely correct. That the NSA is empowered to spy on Americans' communications without a warrant – in direct contravention of the core Fourth Amendment guarantee that "[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause" – is the dirty little secret of the U.S. Surveillance State.