In brief: For at least a year, the FBI had conducted unauthorized searches of US citizens via an NSA database. Last year, the secret court that oversees FISA applications ruled that the agency violated the law and the Fourth Amendment in its accessing of that information. That ruling was just declassified today.

A top-secret ruling by the Foreign Intelligence Surveillance Court (FISC) deemed that the Federal Bureau of Investigation violated the Fourth Amendment rights of tens of thousands of US citizens. The Office of the Director of National Intelligence (ODNI) published the declassified FISC opinion on Tuesday.

The heavily redacted October 2018 documents shows that between 2017 and 2018, the FBI inappropriately used Section 702 of the Foreign Intelligence Surveillance Act (FISA) to gain certifications to search a surveillance database maintained by the National Security Agency. Agents accessed information on US citizens, including emails, phone numbers, and other identifying information.

According to the Wall Street Journal, some of the searches were frivolous such as agents looking up themselves, friends, family, and coworkers. The FISC ruled that these actions were in clear violation of the Fourth Amendment since none of the searches had attached warrants.

"Initially, the FISC approved most aspects of the 2018 Certifications but found that certain parts of the Federal Bureau of Investigation's (FBI) procedures concerning the querying of United States persons were not sufficient." --- ODNI statement

Furthermore, Section 702 of the FISA limits the use of the NSA's database to searches for evidence of a crime in an ongoing investigation into a foreign national. Usually, these queries are part of terrorism of cyberthreat probes.

Hearings before the FISC to grant such searches are held in private and are considered top secret due to the sensitivity of these investigations. It is for this reason that the court holds a much higher standard for issuing warrants.

The ruling took a year to become public because the FBI fought the decision in front of the Foreign Intelligence Surveillance Court of Review (FISC-R), which is like the appellate arm of the FISA Court. However, the FISC-R upheld the initial ruling that the FBI violated both Section 702 and the Fourth Amendment.

The FBI must now draft new oversight procedures. It must also form a "compliance review team" to ensure that the agency does not abuse its surveillance powers going forward.