Cory Bennett explains that the Deep State could easily have have initiated surveillance on its own with no explicit permission from the White House. This would, of course, in no way preclude the use of the fruits of such surveillance by persons affiliated with Barack Obama against the Trump Administration and Trump appointees.

[T]here are still many ways in which information from Trump Tower phone calls could end up in the hands of intelligence agents or law enforcement officials — even without any knowledge on Obama’s part.

First, they may have come upon Trump Tower phone calls if a targeted foreign agent was on the other end of the line — this method comes from the Foreign Intelligence Surveillance Court, or FISA court. Or Trump Tower digital chatter might have shown up while authorities dug through the vast quantities of data hoovered up via more sweeping foreign surveillance programs.

Second, the FBI could also have asked for a so-called “pen register” or “trap and trace device,” which record only the parties involved in a phone call. These requests have a lower bar for approval.

While it’s unknown whether any of these scenarios occurred, it’s “very likely that the people in the Obama administration had access to the communication of senior Trump officials in the run-up to the election, because they have very, very broad authority,” said Cindy Cohn, executive director of the Electronic Frontier Foundation, which has advocated for revising surveillance laws.

And given the ongoing FBI-led investigation into potential ties between Trump’s associates and Russian officials, it’s plausible that law enforcement officials and intelligence agencies had an interest in — or simply came across — the communications in Trump Tower, specialists said. The government is also investigating an alleged Russian plot to use cyberattacks and disinformation to help Trump win.

According to news reports, the FBI last summer went to the FISA court — which approves clandestine spying efforts — asking for warrants to monitor four members of Trump’s team suspected of having improper exchanges with Russian officials. After being rebuffed, officials reportedly narrowed their request and got approval in October to monitor a computer server in Trump Tower to establish whether there were ties to Russian banks.

But such surveillance would be vastly different than the type of direct wiretapping Trump raised in his tweetstorm Saturday morning.

Nojeim explained that government investigators have two routes to obtaining a wiretap in the U.S. — one for criminal probes, one for intelligence gathering.

On the criminal side, the government must present a judge with probable cause that a wiretap-eligible offense has occurred — or is occurring — and that a wiretap will uncover the necessary evidence. Wiretap-eligible offenses are numerous, and they run the gamut from bribing witnesses to more opaque ones like “fraud by wire.”

The other route is through the FISA court, where the hurdles are trickier, specialists said, because the spying programs it oversees focus on foreign targets.

Officials must present the FISA court judge with probable cause that the person being wiretapped is an agent of a foreign power, like a spy, or an agent of a foreign terrorist organization. The government must also show that the phone line, email account or computer server in question is going to be used by that foreign target. If that target is an American citizen, the attorney general also has to OK the spying.

“There is a significant hurdle to wiretapping a person in the United States under either of these authorities,” Nojeim said.

Indeed, senior U.S. officials with knowledge of the government’s investigation into Russia’s alleged digital meddling with the U.S. election told The Washington Post there had been no wiretap of Trump.

But surveillance experts — and especially surveillance critics — were quick to note the myriad other routes officials have to get at the banter inside Trump Tower.

Through routine data collection programs authorized under Section 702 of the Foreign Intelligence Surveillance Act, the government gathers information from the internet backbone, which carries web browsing histories and a rapidly increasing amount of telephone traffic.

The government discards information that is plainly domestic and searches through the rest using only specific selectors — a phone number or email address, for instance. But Americans’ information that is incidentally collected and determined to contain some foreign intelligence value is fair game for review.

Cohn said such data on Americans could include communications that are to, from or about foreign targets the FISA court has already approved for surveillance. For example, if two Trump campaign officials were talking via email about a Moscow official under surveillance, that conversation might get flagged as relevant.

Trump’s anger over the potential surveillance of him and his campaign is only likely to increase people’s awareness of these programs, some of which are up for reauthorization at the end of 2017.

The White House reportedly supports a “clean” reauthorization with no revisions. But the heightened attention to the topic has already been used in Capitol Hill hearings to argue for an overhaul of the laws.

“I think that even if [Trump is] not exactly right about what happened here, the fact that he could tweet this … and we can’t tell exactly what happened, means that we need to have an honest conversation in this country about these authorities,” Cohn said.