Ed and Elaine Brown let the marshals into their secluded Plainfield compound about 7:45 p.m. Thursday, U.S. Marshal Stephen Monier said.
"Ultimately, this open-door policy that they seemed to have -- which allowed the Browns to have some supporters bring them supplies, welcome followers and even host a picnic -- this proved to be their undoing," Monier said. "They invited us in. We escorted them out."
Monier said no one else was in the Browns' home when the undercover agents entered. "This ended exactly the way we wanted it to end," he said, "without a shot being fired and with no one getting hurt."
Authorities discovered a large number of weapons, explosives and ammunition on the property, Monier said, and booby traps had been set up along the perimeter of the house.
The couple were turned over to the custody of the U.S. Bureau of Prisons, Monier said. Each is expected to serve a 63-month sentence.
The Browns stopped paying income taxes in 1996, saying that the Constitution and Supreme Court decisions supported their claims that ordinary labor cannot be taxed. Ed Brown, a former exterminator, had repeatedly demanded, "Show me the law!"
But a judge ruled against them in January, convicting the Browns of conspiring to evade paying taxes on $1.9 million in income from Elaine's dentistry practice. Ed, 65, immediately went into hiding, and Elaine, 67, joined him after both failed to show up for their sentencing in April.
Government and law enforcement officials cut off power, Internet, telephone, cellphone, television and mail service to the couple's 110-acre compound. But the Browns had equipped it with solar panels, a watchtower, a satellite dish and a stockpile of food.
The couple had attracted national attention from websites and radio shows devoted to discussing their cause. Supporters held fundraiser concerts on the Browns' property and set up a blog and MySpace page for them. Last month, authorities arrested four men accused of assisting the Browns.
Shaun Kranish, a supporter from Rockford, Ill., who had visited the Brown home, said that he was discouraged by their arrests and that he found it hard to believe they had not put up a fight.
"We were not told," he said, "how or what types of weaponry were involved in taking them."