PORTLAND, Ore. — Armed antigovernment protesters led by Ammon and Ryan Bundy were acquitted Thursday of federal conspiracy and weapons charges stemming from the takeover of a federally owned wildlife sanctuary in Oregon last winter.

The surprise acquittals of all seven defendants in Federal District Court were a blow to government prosecutors, who had argued that the Bundys and five of their followers used force and threats of violence to occupy the reserve. But the jury appeared swayed by the defendants’ contention that they were protesting government overreach and posed no threat to the public.

In a sign of the tension that ran through the trial, Ammon Bundy’s lawyer, Marcus R. Mumford, frustrated that the Bundys were not being released, was restrained by four United States marshals after an outburst.

“I knew that what my husband was doing was right, but I was nervous because the judge was controlling the narrative,” said Ryan Bundy’s wife, Angela Bundy, 39, in a telephone interview from the family ranch in Bunkerville, Nev. “But they saw the truth. I am just so grateful they saw it.”