Ed and Elaine Brown, both in their 60s, face a mandatory minimum 30-year prison sentence on one charge alone.
The Browns holed up in their hilltop home in New Hampshire in early 2007 to avoid arrest after being convicted of tax evasion. They amassed an arsenal of high-powered weapons and explosives, including booby-traps in woods surrounding the home.
During the trial, Ed Brown testified that the weapons were for self-defense, saying he believed the government planned to kill him and his wife. The two were arrested in October 2007 without incident.
In court Thursday, the couple held hands and looked straight ahead as the verdict was read. They refused to stand when the jury and judge left the courtroom. Defense lawyers declined to comment.
The prosecution denounced the Browns' behavior behind their crimes.
"By rejecting the rule of the law and substituting a personal code involving weapons, explosives and threats, the defendants committed increasingly serious crimes," acting U.S. Attorney Michael Gunnison said. "Their conduct has no place in a civil society."
The Browns are scheduled to be sentenced on Sept. 3.
The verdict came after seven hours of deliberation over two days.