After President Richard Nixon was forced from office in 1974, congressional investigators discovered what they believed was the full extent of his use of the FBI and the CIA to engage in domestic spying. In that pre-digital era, the spying consisted of listening to telephone calls, opening mail, and using undercover agents to infiltrate political organizations and, as we know, break into their offices. Nixon claimed he did this for the protection of national security. He also claimed he was entitled to break the law and violate the Constitution. “If the president does it, that means that it’s not illegal,” he once famously said.

Since no one was prosecuted on the basis of data stolen or retrieved by his spies, the courts rarely encountered this behavior and never had to rule on it, and thus it went largely unchecked. A few victims challenged the spying, but the Supreme Court ruled that without palpable harm, the challengers lacked the legal ability to complain in court -- what judges call “standing.”

But many Americans did complain to Congress, which in 1978 enacted the Foreign Intelligence Surveillance Act, commonly called FISA. FISA provided that all domestic surveillance be subject to the search warrant requirement of the Fourth Amendment, except for spying on foreign agents operating in the U.S. For those cases, FISA established a secret federal court that has been authorized to issue search warrants to spy on foreign agents.

The constitutional standard for all search warrants is probable cause of crime. FISA, however, established a new, different and lesser standard -- thus unconstitutional on its face since Congress is bound by, and cannot change, the Constitution -- of probable cause of status. The status was that of an agent of a foreign power. So, under FISA, the feds needed to demonstrate to a secret court only that a non-American physically present in the U.S., perhaps under the guise of a student, diplomat or embassy janitor, was really an agent of a foreign power, and the demonstration of that agency alone was sufficient to authorize a search warrant to listen to the agent’s telephone calls or read his mail.

Over time, the requirement of status as a foreign agent was modified to status as a foreign person. This, of course, was an even lesser standard and one rarely rejected by the FISA court. In fact, that court has rarely rejected anything, having granted search warrants in well over 97 percent of applications. This is hardly harmless, as foreign persons in the U.S. are frequently talking to Americans in the U.S. Thus, not only did FISA violate the privacy rights of foreigners (the Fourth Amendment protects “people,” not just Americans); it violated the rights of those with whom they were communicating, American or non-American.

It gets worse. The Patriot Act, which was enacted in 2001 and permits federal agents to write their own search warrants in violation of the Fourth Amendment, actually amended FISA so as to do away with the FISA-issued search warrant requirement when the foreign person is outside the U.S. This means that if you email or call your cousin in Europe or a business colleague in Asia, the feds are reading or listening, without a warrant, without suspicion, without records and without evidence of anything unlawful.

The Patriot Act amendments to FISA also permit the feds to use anything they see or hear while spying in a federal court. The amended FISA statute permitting these warrantless searches of emails, telephone calls and postal mail expires at the end of this month. Last month, the House quietly voted to extend this dreadful authority for another five years, and in the next week, the Senate will consider doing the same.

What’s wrong with Congress?

FISA gives the government unchecked authority to snoop on all Americans who communicate with any foreign person, in direct contravention of the Fourth Amendment. The right to privacy is a natural human right. Its enshrinement in the Constitution has largely kept America from becoming East Germany. Moreover, everyone in Congress has taken an oath to uphold the Constitution, which could not be more clear: “The right of the people to be secure in their persons, houses, papers, and effects…” shall not be violated, except via a warrant issued by a neutral judge upon the judge finding probable cause of crime. If we let Congress, which is a creature of the Constitution, change the Constitution, then no one’s liberty or property is safe, and freedom is dependent upon the political needs of those in power.

The president and the leadership of both political parties in both houses of Congress have abandoned their oaths to uphold the Constitution. They have claimed that foreigners and their American communicants are committed to destroying the country and only the invasion of everyone’s right to privacy will keep us safe. They are violating the privacy of us all to find the communications of a few. Who will keep us safe from them? Their behavior is committed to destroying the Constitution.

Andrew P. Napolitano, a former judge of the Superior Court of New Jersey, is the senior judicial analyst at Fox News Channel. Judge Napolitano has written seven books on the U.S. Constitution. His latest is “Theodore and Woodrow: How Two American Presidents Destroyed Consti...