WASHINGTON — In two unsigned decisions without noted dissents, the Supreme Court on Monday ruled in favor of police officers accused of using excessive force. The rulings were a signal that the court continues to support the doctrine of qualified immunity, which can shield police misconduct from lawsuits seeking damages.

The doctrine has been the subject of criticism across the ideological spectrum, and it became a flash point in the nationwide protests last year over police brutality, with activists and lawmakers calling for its reconsideration.

The doctrine requires plaintiffs to overcome a daunting hurdle. They must not only show that the official accused of misconduct violated a constitutional right, but also that the right had been “clearly established” in a previous ruling. The Supreme Court has generally required a tight factual fit between an earlier ruling and challenged conduct.

Critics of the doctrine were heartened by two rulings this year that called on appeals courts to reconsider rulings in favor of corrections officers accused of mistreating prisoners. One prisoner was held in what the court called “shockingly unsanitary cells,” and the other was sprayed in the face with a chemical “for no reason at all.”

Some cases are so egregious, the court suggested, that no precedent directly on point was necessary to allow a plaintiff to sue.

The decisions on Monday, which concerned police officers rather than prison guards, took a different approach. One arose from a 911 call reporting that a woman and her two children were barricaded in a room in Union City, Calif., fearing that Ramon Cortesluna, the woman’s boyfriend, would break in and hurt them.

Five officers responded, ordering Mr. Cortesluna to come outside, raise his hands and get on his knees. He complied at first but later dropped his hands, and the officers noticed a knife in his back pocket. An officer shot him in the stomach and left hip with nonlethal beanbag rounds.

The U.S. Court of Appeals for the Ninth Circuit, in San Francisco, ruled that those shots “were objectively reasonable in the circumstances.”

The appeals court took a different view of what followed. After Mr. Cortesluna was shot, he was ordered to get down. He did, lying prone on his stomach.

Officer Daniel Rivas-Villegas then straddled Mr. Cortesluna, putting his left knee on the left side of Mr. Cortesluna’s back for what the Supreme Court opinion said was “no more than eight seconds.” Another officer removed the knife and handcuffed him.

The Ninth Circuit allowed Mr. Cortesluna’s excessive force lawsuit against Mr. Rivas-Villegas to proceed, saying the officer had been on notice that putting his knee on a prone man’s back with enough force to injure him was unlawful.

The Supreme Court disagreed. “Neither Cortesluna nor the court of appeals identified any Supreme Court case that addresses facts like the ones at issue here,” the court said its unsigned opinion in the case, Rivas-Villegas v. Cortesluna, No. 20-1539. A previous decision by the Ninth Circuit, the justices added, did not address sufficiently similar facts.

That decision concerned a man who was injured after the police responded to a noise complaint. In that case, the Supreme Court opinion said, “the officer deliberately dug his knee into his back when he had no weapon and had made no threat when approached by police.”

The second decision on Monday, in City of Tahlequah v. Bond, No. 20-1668, also arose from a 911 call, this one in Tahlequah, Okla., reporting that a woman’s ex-husband was drunk in her garage and would not leave.

When three officers arrived, Dominic Rollice, the ex-husband, brandished a hammer. Officers Josh Girdner and Brandon Vick fired their weapons, killing Mr. Rollice. His estate sued, and the Tenth Circuit, in Denver, let the case proceed, ruling that a jury could find that the officers were not entitled to qualified immunity because previous rulings had put them on notice about creating circumstances that could lead to the shooting.

The Supreme Court ruled that the appeals court had not identified any earlier decision that “comes close to establishing that the officers’ conduct was unlawful.”

More generally, the court said that qualified immunity was a rigorous standard.

“It is not enough that a rule be suggested by then-existing precedent,” the court wrote. “The rule’s contours must be so well defined that it is clear to a reasonable officer that his conduct was unlawful in the situation he confronted.”