The exterior of the J. Edgar Hoover Building, the FBI headquarters, in Washington. (Matt McClain)

Geoffrey Stone is a law professor at the University of Chicago. Michael Morell was the deputy director of the CIA from 2010 to 2013 and twice served as acting director.

Congress is about to make a major decision about privacy protection, civil liberties and national security. The 2008 Foreign Intelligence Surveillance Amendments Act, including its most controversial provision, Section 702, is set to expire on Dec. 31. The two of us — both members of the panel that President Barack Obama appointed in 2013 to review the government's foreign intelligence programs in the wake of Edward Snowden's disclosures — agree that FISA Section 702 should be reauthorized but with a significant reform. The government should no longer be permitted to search the data collected under Section 702 without a warrant when seeking information about U.S. citizens and legal permanent residents.

Section 702 permits the government to conduct targeted surveillance of foreign people located outside the United States. This statute is necessary because a significant share of the world's communications transits through the United States, even when they begin and end overseas. Congress enacted Section 702 to address an intelligence-collection gap that resulted from the evolution of technology in the years after FISA became law in 1978. By 2008, many foreign intelligence targets outside the United States were using communications systems based in the United States, especially those provided by U.S.-based Internet service providers.

Traditionally, a court order was required for the government to intercept any communications inside the United States. Because of the change in technology, and before FISA was amended in 2008, court orders were therefore required for the government to target foreigners who were outside the United States if their communications flowed into the United States. This was required neither by the Fourth Amendment nor by common sense but was simply the accident of new technology. Section 702 was designed to remedy this situation.

It is important to note that Section 702 surveillance is permitted only to acquire foreign intelligence information from non-Americans who are overseas. Section 702 may not be used to target Americans anywhere in the world. It may not be used to target anyone located inside the United States, regardless of nationality. And it may not be used to target a foreign individual when the intent is to acquire the communications of an American with whom a foreign person is communicating.

When we reviewed the program in 2013, we found it to be one of our nation's most effective programs to protect our national security. Operations under Section 702 generate important intelligence on international terrorists, individuals and entities involved in the proliferation of weapons of mass destruction, those engaged in espionage, and people and groups conducting illicit cyber-activities. We also found that the government works conscientiously to implement this program in a manner that protects the privacy of American citizens and legal U.S. residents. It is for these reasons that we urge Congress to reauthorize Section 702.

There is, however, one aspect of the way the 702 program has evolved that we believe needs to change: the FBI's practice of searching the data for information on Americans without first obtaining a warrant. Section 702, like any surveillance program, incidentally and inadvertently collects communications of or about individuals who are themselves not the target of intelligence collection. That is, the program will inevitably sometimes pick up communications between the target and an American, and it sometimes will pick up targets talking about Americans. The government argues that because such information was legally acquired, it should be able to search the information without first obtaining a warrant.

We disagree, except in the case of specifically outlined emergencies such as an imminent terrorist threat. Americans are entitled to full protection of their privacy. They should not lose that protection merely because the government has information in a foreign intelligence database that it legally acquired. Importantly, the government collected that information by using a standard that could not be legally be employed to target an American anywhere in the world.

Section 702 should be used in the way it was designed — to obtain information about foreign targets while preserving the privacy of Americans. It should not offer an easy route for federal law enforcement agents, specifically the FBI, to obtain evidence about Americans to which they would not be otherwise entitled. We urge Congress to end this practice. Such a step would reduce any incentives for government agents to misuse Section 702 without harming legitimate surveillance of foreign nationals operating overseas.