WASHINGTON — In a surprising setback to regulators’ efforts to interrupt up Fb, a federal decide on Monday threw out antitrust lawsuits introduced in opposition to the corporate by the Federal Commerce Fee and greater than 40 states.

The decide, James E. Boasberg for the U.S. District Courtroom for the District of Columbia, said the case from the states needed to be dismissed as a result of an excessive amount of time had elapsed because the alleged offenses passed off. The states, led by Letitia James, the New York lawyer basic, accused Fb in December of shopping for up nascent opponents like Instagram and WhatsApp — offers made in 2012 and 2014 — to cement its monopoly over social networking.

In a separate, 53-page opinion, he mentioned the complaint by the Federal Trade Commission, additionally filed in December, failed to offer sufficient information to again its claims that Fb had a monopoly over private social networking.

The decide mentioned that the F.T.C. had 30 days to refile its criticism.

“This actually stings,” mentioned William E. Kovacich, a former chairman of the company. “This can be a reminder to those that have wished a dramatic, sweeping litigation marketing campaign to tackle Large Tech that there’s nothing straightforward about it, as a result of the courts have a special view of the antitrust system.”

Representatives for the F.T.C. and the New York lawyer basic didn’t instantly have feedback.

Christopher Sgro, a spokesman for Fb, mentioned: “We’re happy that at present’s choices acknowledge the defects within the authorities complaints filed in opposition to Fb. We compete pretty on daily basis to earn folks’s time and a spotlight and can proceed to ship nice merchandise for the folks and companies that use our providers.”

The information pushed Fb’s replenish 4.2 %, and the corporate handed $1 trillion in market capitalization, a primary for the social community and one among solely half a dozen corporations to succeed in such a valuation.

The choice was a serious blow to bipartisan makes an attempt in Washington to rein in Large Tech. President Biden has put in critics of the know-how giants in key regulatory roles, together with Lina Khan as chair of the F.T.C., and he’s anticipated to concern broad mandates this week for federal businesses to handle company focus throughout the financial system. Ms. Khan’s first main job as chair can be to rewrite the lawsuit to handle the decide’s criticisms.

In Congress, legislators pointed to the selections as proof that century-old antitrust legal guidelines wanted updating for the web sector. Courts have narrowed interpretations of antitrust legal guidelines through the years, making authorities instances troublesome to win. Final week, the Home Judiciary Committee advanced six bills that will overhaul antitrust legal guidelines, with the aim of loosening the grips that Amazon, Apple, Fb and Google have over extensive swaths of the financial system.

“Right now’s improvement within the F.T.C.’s case in opposition to Fb reveals that antitrust reform is urgently wanted,” mentioned Consultant Ken Buck, a Republican from Colorado and a co-sponsor of the antitrust payments. “Congress wants to offer further instruments and sources to our antitrust enforcers to go after Large Tech corporations partaking in anticompetitive conduct.”

Republican Senator Josh Hawley of Missouri, a critic of Large Tech, mentioned on Twitter that the courtroom had acknowledged Fb’s “large market energy however basically shrugged its shoulders.”

The choice was additionally a disappointment for the rising cohort of activists who’ve pushed regulators to maneuver to interrupt up the largest tech corporations. Sarah Miller, the manager director of the antitrust suppose tank the American Financial Liberties Challenge, mentioned she hoped the states would enchantment the dismissal and the F.T.C. would file its case once more. However she mentioned the decide’s ruling underscored the necessity for Congress to replace the legal guidelines that police market focus.

“The courts are going to wish, ideally, some congressional steerage right here, provided that they’ve some outsized function in figuring out the outcomes of antitrust instances,” she mentioned. “Typically losses might be good as a result of it may well simply reinforce that necessity, and we’re hoping that this can serve to do this.”

This can be a creating story. Verify again for updates.

David McCabe contributed reporting.