Last week, President Trump tweeted that President Obama wiretapped him during the 2016 presidential campaign. That’s probably not true. Since the intelligence reforms of the 1970s, it’s been unlawful for presidents to order targeted wiretapping of Americans. Only prosecutors can do that, and with judicial approval.

While Trump likely got it wrong on the details, he’s not wrong in a broader sense: It’s far too easy for the United States government to wiretap Americans’ communications, and that’s thanks in part to President Obama’s actions in office. But if Trump is really concerned about the government’s legal authority to wiretap Americans—including him—he can do something about it when a major post-9/11 surveillance law is up for reauthorization at the end of this year.

Some historical background is required to understand the significance of Trump’s comments, and the upcoming congressional battle over warrantless spying.

In 1978, Congress passed Senator Ted Kennedy’s bill to rein in domestic surveillance, the Foreign Intelligence Surveillance Act (FISA). Signed into law by President Carter, the statute was the government’s answer to explosive revelations about domestic spying unearthed by the 1971 FBI robbers, Senator Frank Church’s congressional committee investigations, and the press throughout the preceding years. The FISA created a new kind of intelligence oversight regime—one that would largely function behind closed doors, out of sight of the vast majority of the American public. But despite the secrecy, the law was an improvement, as it for the first time required intelligence agencies to answer to congressional committees and submit surveillance requests to a new judicial body, the Foreign Intelligence Surveillance Court (FISC).

After 9/11, the Bush administration secretly began flouting the FISA by allowing the NSA to conduct warrantless wiretapping of Americans’ international communications. New York Times reporter James Risen found out about the warrantless spying programs before the 2004 election, but the Times didn’t publish the explosive revelations until 2005, after Bush had already secured his second term in office.

In 2008, Congress passed the FISA Amendments Act (FAA), greatly expanding surveillance powers. Inside that bill was a provision called Section 702, which put congress’ stamp of approval on the Bush warrantless wiretapping scheme. In one of his last acts as a Senator, Barack Obama voted for the controversial proposal. In one of his last acts in office, President Bush signed it into law. The ACLU immediately filed suit to challenge the constitutionality of Section 702.

In 2012, President Obama pushed hard for the reauthorization of the FISA Amendments Act. On December 31^st, New Years Eve 2012, Obama signed the reauthorization bill into law, extending the Bush administration’s warrantless wiretapping authority for another five years—to 2017.

Just a few months after Obama extended the law another five years, in February 2013, the Supreme Court ruled in favor of the government in the ACLU’s lawsuit, holding that the ACLU’s clients lacked standing to challenge the law because they couldn’t prove that the government had used Section 702 authorities to warrantlessly wiretap them. Just months later, in June of that year, documents leaked by former NSA contractor Edward Snowden were published on the Guardian’s website, exposing headline-grabbing government deceit, dragnet surveillance, and something called the PRISM program. PRISM, we learned, was authorized under Section 702.

That statute, which is up for reauthorization at the end of 2017, provides the US government with expansive authorities to monitor the communications of US persons without warrants. It also allows domestic law enforcement to use information obtained without warrants in domestic criminal investigations and prosecutions.

Here are three facts about Section 702 that you, Donald Trump, and every other American should know as the battle to reauthorize the law heats up this year.

1. The statute forbids the ‘targeting’ of US person communications, but allows investigators to collect, retain, search for, and use information against people who aren’t ‘targets.’ Under Section 702, the NSA can wiretap your international phone and electronic communications without warrants as long as the agency is ‘targeting’ the person you’re talking to outside the country, not you. The spies know this setup allows them to collect large quantities of US person communication data. Prior to 2011, they weren’t supposed to rifle through that information looking for data about particular US citizens. In 2011, that changed when the NSA convinced the FISC to allow them to conduct these so-called ‘backdoor searches.’ Now, the NSA and the FBI can search through Section 702 data—which includes PRISM information—looking for information about you, even if you’re not suspected of a crime.
2. The FBI can use information the NSA obtained about you without warrants. When talking about dragnet spying, we often focus on the role of the agency doing the most collecting: the NSA. But the FBI plays a critically important part, particularly where Americans’ privacy rights are concerned. Section 702 allows the NSA to create massive databases full of Americans’ communications, all obtained without individual court orders or even suspicion that the persons monitored are involved in crimes. That’s bad enough. But even worse, the FBI has the power to type your name, email address, IP address, phone number, or other “identifier” into that database, looking for your warrantlessly wiretapped communications. Worse still, the FBI can then use those communications against you in domestic criminal investigations and prosecutions. As former Privacy and Civil Liberties Oversight Board Chairman David Medine said, “the FBI has absolutely no suspicion of wrongdoing … they’re just sort of entitled to poke around [in Americans’ communications obtained via Section 702] and see if something is going on.”
3. We don’t know how many Americans have been warrantlessly wiretapped by the NSA, because the Office of the Director of National Intelligence (ODNI) refuses to tell us. In 2012, Senator Ron Wyden sponsored an amendment to the FISA Amendments Act reauthorization bill which would have required the ODNI to report on how many Americans are monitored under the law, and provide information about how those communications are reviewed, searched, or used. The amendment failed by a 52-43 vote. In a February 2017 Congressional hearing, former NSA employee April Doss told members of the House Judiciary Committee that the NSA couldn’t produce information showing how many Americans had been monitored under Section 702 because doing so would violate their privacy rights.

If you think this is outrageous, call your representatives in Congress and tell them that while Obama probably didn’t order surveillance on Trump tower, there is a real surveillance scandal in the United States: the NSA’s warrantless wiretapping, and the FBI’s warrantless use of that information.