In an effort to draw attention away from the intelligence failures that permitted the attacks of 9/11 and create the impression that it was doing something -- anything -- to avoid a repeat, the federal government tampered seriously with freedoms expressly guaranteed in the Constitution. Its principal target was the right to privacy, which is protected in the Fourth Amendment.

At President George W. Bush’s urging, Congress passed the Patriot Act in October 2001. This 315-page statute passed the House of Representatives with no debate, and there was very limited debate in the Senate. I have asked many members of Congress over the years whether they read this bill before they voted upon it, and I have yet to find a member who did. In the House, that would have been impossible; the bill was made available to representatives only 15 minutes prior to their vote.

This law permits FBI agents to write their own search warrants for business records, and it has been used to induce the Foreign Intelligence Surveillance Court to issue warrants on a made-up basis to read emails and listen to telephone calls in real time. The members of Congress who voted for it were largely unaware of the liberties they were sacrificing.

The personal liberties that Congress surrendered have been a necessary bulwark against tyranny -- the constitutional requirement of warrants as a precondition to searching homes and records, with warrants based on probable cause and specifically describing the place to be searched and the person or thing to be seized.

The personal liberties that Congress surrendered have been a necessary bulwark against tyranny -- the constitutional requirement of warrants as a precondition to searching homes and records, with warrants based on probable cause and specifically describing the place to be searched and the person or thing to be seized.

When Edward Snowden revealed the nature and extent of the domestic spying that the government unleashed upon us post-9/11 and made us all aware of its use of the Patriot Act to do so, the authors of the Patriot Act expressed outrage and anger.

            What was the government doing?

            The government was secretly gathering data on all of us and using warrants that were not based on probable cause and that did not specifically describe the place to be searched or the person or thing to be seized. When members of Congress realized that they, too, were being spied upon, the outrage grew. That outrage and anger metastasized into a new law enacted earlier this year, called the USA Freedom Act, which took effect this week. That law, its supporters have argued, will tame the National Security Agency into constitutional compliance and keep its 60,000 agents and contractors out of our private affairs. In fact, it is now worse.

            The new law permitted the expiration of Section 215 of the Patriot Act -- the section used by the NSA to justify its collection of undifferentiated bulk data about everyone. But it also requires the telecoms and Internet service providers to retain their records for five years, and it gives the NSA instant access to those records whenever it needs them.

            How can the NSA get instant access to your emails and phone calls?

            Quite easily. Both the Patriot Act and the USA Freedom Act unconstitutionally do away with the probable cause requirement for warrants. Those two laws permit the Foreign Intelligence Surveillance Court to issue warrants based on the standard of “governmental needs” rather than probable cause. This is a profoundly unconstitutional standard, and one that has resulted in spying on all people all the time.

            In reality, "governmental needs" is no standard whatsoever, as the government will always claim that it needs what it wants. "Governmental needs" is the hateful standard that was used by the British government when it secretly obtained warrants to enter the homes of the colonists. This provoked the Revolution and produced the Fourth Amendment.

            Though Section 215 of the Patriot Act has expired, the NSA’s other authorities to spy have not. The propaganda that NSA computers have been shut down is false. Its computers are still in the telecom and Internet service providers’ facilities and are operated by NSA agents remotely.

            Nevertheless, Section 702 of the Foreign Intelligence Surveillance Act and an October 2001 executive order by President Bush are still valid, and both bypass the Constitution and continue to permit mass collection of bulk data. Section 702 permits warrantless surveillance on Americans who speak with foreigners, and the NSA has persuaded the FISA court to issue warrants to intercept the calls of the folks to whom those Americans speak, to the sixth degree. That alone encompasses everyone in the United States.

            The Bush executive order was given to all military intelligence agencies -- of which the NSA is but one. It instructed the military to intercept the telephone calls of anyone in America it wishes, without seeking any warrants.

            Does all this unconstitutional spying -- whether pursuant to the Patriot Act, the USA Freedom Act or an old presidential executive order -- keep us safe? It certainly does not keep our liberties safe. It produces too much material for the government to evaluate. The recent Paris killers communicated with one another using ordinary cellphones and emails. Yet the French government, whose legal authority to spy is broader than our government's, missed them. And the NSA, which spies on the French government, missed them.

            The Fourth Amendment has numerous virtues, but foremost among them is a double-sided coin. One side is the requirement of individualized probable cause. When followed, that prevents the government from using general warrants (search wherever you want, and seize whatever you find), the hallmark of totalitarian governments. By confining the government’s authority to search only to those cases about which it has suspicion, the other side of that coin forces the government to focus on the bad guys.

            When it does that, the government will be far likelier to stop them than when it gathers all it can about everyone.

Andrew P. Napolitano, a former judge of the Superior Court of New Jersey, is the senior judicial analyst at Fox News Channel.