[Zero] In a May 25 letter to FBI Director Christopher Wray, Reps. Jim Jordan (R-Ohio) and Mike Turner (R-Ohio) asked Wray to explain why his agency had wiretapped and gathered personal information on over 3.3 million Americans without a warrant (pdf).Limited authority to gather foreign intelligence information is granted by the Foreign Intelligence Surveillance Act (FISA).
Specifically, section 702 of the bill says: "the Attorney General (AG) and the Director of National Intelligence (DNI) may jointly authorize the targeting of (i) non-U.S. persons (ii) who are reasonably believed to be outside of the United States (iii) to acquire foreign intelligence information."
However, this power can grant an expanding circle of possible searches to the FBI and other intel agencies, who can use the same power against American citizens who had any interaction with targeted foreigners.
Historically, insight into how FISA has been used against American citizens has been limited and hidden behind classified reports.
However, a November 2020 decision by the Foreign Intelligence Surveillance Court (FISC)—which serves as a watchdog for U.S. intelligence agencies—required that the Office of the Director of National Intelligence (ODNI) report "the number of U.S. person queries run by the FBI against Section 702-acquired information."