The Republic of Idaho is the main faction fighting against the federal government after Idaho secedes from the union.
When Laura Griffith became president, she declared Idaho to be in a state of rebellion and orders the United States military to end it. She orders all Idaho military, law enforcement, and militia personnel to unconditionally surrender immediately and that Idaho residents should disarm, remain in their homes, and obey all instructions from federal authorities. These demands are non-negotiable and not open to debate. Griffith then shuts down Idaho's electricity and suspends their rights. The Federal Idaho Reconstruction Authority is called in to enforce the Federal ID Card Act.
Around Christmas time 2021, James Montaine announced that despite the Federal invasion, Southern Idaho is liberated thanks to the Brotherhood of the White Eagle. Northern Idaho however faces harsh occupation from FIRA forces. After President Griffith designated Idaho a rebel state, Montaine and the state legislature declares the state to become the fully independent Republic of Idaho, dissolving all former ties with the United States. He then invokes Article XIV Section 1 which reads:
All able-bodied male persons, residents of this state, between the ages of eighteen and forty-five years, shall be enrolled in the militia, and perform such military duty as may be required by law; but no person having conscientious scruples against bearing arms, shall be compelled to perform such duty in time of peace.
This act of defiance later on encourages the states of Texas, Oklahoma, Wyoming, and Montana to secede the Union.