Today the Senate takes up a bipartisan surveillance authorization measure that’s already passed the Intelligence Committee. The clock is ticking. This Friday a temporary law called the Protect America Act will expire. If Congress does not act before then, the president’s statutory power to prevent terrorist attacks will be seriously compromised.

This dangerous situation should never have arisen. From the beginning, presidents have exercised their Article II executive power to gather foreign intelligence — in war and peace alike, without congressional or judicial intrusion. As our principal agent in foreign affairs, the president is constitutionally bound to protect the nation. For that, intelligence is essential.

Intelligence is essential on the domestic side as well, where law enforcement is the president’s main function. Yet not until 1967 did the Supreme Court require warrants for electronic surveillance. Congress codified that a year later. But both the court and Congress expressly exempted foreign-intelligence gathering from the warrant requirement.

Unfortunately, the exception was not to last. Following the Vietnam War, Congress increasingly inserted itself into foreign affairs, as with the 1973 War Powers Act. With the Foreign Intelligence Surveillance Act, passed in 1978, Congress began micromanaging foreign intelligence gathering. That produced the “wall” between foreign and domestic intelligence gathering — with foreign-intelligence agents focused on security, and domestic agents on prosecution and hence on obtaining “admissible” evidence. Neither side talked to the other. Many believe the resulting communications failures played a role in 9/11.

In the aftermath of 9/11, believing FISA to be hopelessly inadequate, President Bush instituted his terrorist surveillance program (TSP) — but not before advising key members of Congress. Nevertheless, a firestorm ensued when the New York Times made the program public in December 2005. The controversy continued until January 2007, when the White House announced that henceforth it would gather intelligence under FISA’s antiquated restrictions.

Cooler heads in Congress grew concerned after Director of National Intelligence Michael McConnell testified in July that “we’re actually missing a significant portion of [the intelligence] we should be getting.” That led to last August’s six-month fix, which expires this week.

Obviously, this is no way to conduct the serious business of foreign intelligence. The ever-changing rules — criminalizing transgressions — leave officials playing it safe in a world of risks.

The Senate bill would be an improvement, not least because it provides retroactive liability protection for telecom companies that allegedly assisted the government after 9/11. But the deeper problem is the very idea of congressional micromanagement.

The Senate bill would require showing probable cause before targeting even U.S. persons abroad, dramatically increasing the role of the FISA court. As Judge Richard Posner wrote on this page two years ago, FISA may be valuable for monitoring communications of known terrorists, “but it is hopeless as a framework for detecting terrorists. It requires that surveillance be conducted pursuant to warrants based on probable cause to believe that the target of surveillance is a terrorist, when the desperate need is to find out who is a terrorist.”

The technical impediments to legislating are even greater. We’re long past alligator clips on copper wires. Today, electronic communication is broken into discrete packets that travel along independent routes before being reassembled. As K.A. Taipale, executive director of the Center for Advanced Studies in Science and Technology Policy, has written, “even targeting a specific message from a known sender requires intercepting (i.e., scanning and filtering) the entire communication flow.” Yet the Senate bill requires that intelligence analysts count the people in the U.S. whose communications were “reviewed,” an all but impossible distraction for analysts already stretched.

Privacy concerns are not trivial. The Constitution protects against “unreasonable” searches. But even with law enforcement, where the main function is ex post prosecution, not ex ante protection, there are numerous exceptions to the Fourth Amendment’s warrant requirement. Yet Congress insists still on micromanaging the president — and he, by failing to assert his authority early on, is now reduced to bargaining with Congress over minutia that will soon be as obsolete and dangerous as the underlying act is today.

John Locke, no sometime civil libertarian, put it well when he observed that the foreign affairs power “is much less capable to be directed by antecedent, standing, positive Laws, than [by] the Executive.” The Federalist’s authors, James Madison, Alexander Hamilton and John Jay, all agreed. The remedy for executive incompetence or recklessness in foreign affairs is political — not legislative, much less legal. Congress, to say nothing of the courts, can no more manage such affairs than it can the economy. What better evidence than these surveillance fits and starts?