Police in riot gear contain a group of protesters at the corner of 12th and L Streets, NW, on the day of President Trump’s inauguration. (Jahi Chikwendiu/The Washington Post)

Prosecutors in D.C. have backed off efforts to prevent Facebook from alerting users when investigators ask to search their political communications. The decision by the U.S. Attorney's office Wednesday came on the eve of a court hearing that had broad implications for the First Amendment rights of Facebook users and others who are politically active online.

A D.C. appeals court was set to consider Thursday morning whether Facebook had to keep quiet when law enforcement investigators sought access to user information. Major U.S. technology companies and civil liberties groups had sided with Facebook in fighting a court order that would have forced the company to stay mum.

Instead prosecutors on Wednesday — in a joint filing with Facebook — told the D.C. Court of Appeals that the nondisclosure orders they were seeking were no longer necessary. The appeals court promptly called off the planned hearing.

The details of the case at the D.C. Court of Appeals have been sealed, but the timing of the investigation and other references in public court documents suggest the search warrants at issue are connected to protests during President Trump's inauguration. About 200 people face felony rioting charges related to demonstrations that damaged property and injured police in downtown Washington Jan. 20.

Facebook turned to the appeals court after a D.C. Superior Court judge in April denied the company's request to get rid of a gag order and told Facebook to turn over "all communications, identifying information and other records" for three accounts.

Prosecutors often ask judges for nondisclosure orders when applying for search warrants because of concerns about tipping off targets who could destroy evidence or undermine an investigation.

The D.C. Court of Appeals had allowed Facebook to make public some details of the sealed case so that the company could enlist legal support from other businesses and organizations. The American Civil Liberties Union, the Electronic Frontier Foundation and a coalition of tech companies say in public filings that Facebook users should have an opportunity to challenge search warrants in court when their rights to engage in anonymous political speech are at issue — and when the public is already aware of an investigation.

The mass arrests on Inauguration Day, for instance, were widely covered by the media.

In the joint filing to dismiss the appeal Wednesday, the U.S. Attorney's office said the gag order was no longer needed because "the investigation at issue in this case has progressed during the pendency of this litigation."

Arthur B. Spitzer, legal Director of the ACLU of the District of Columbia, said in response to the filing: "Now that Facebook is free to notify these three users that their accounts are subject to a search warrant, we hope the users will contact us or other lawyers to challenge the government's attempt to conduct a fishing expedition through their Facebook accounts."