Few know that the Army National Guard has two Special Forces Groups. The 19th SFG (Airborne) and 20th SFG (Airborne) are accessible to civilians and prior military from any branch wishing to undertake the long and arduous path to becoming a Green Beret. Moreover, recently separated Green Berets can also join.
The two Groups run several iterations of the Special Forces Readiness Evaluation (SFRE) course each year in multiple locations. Those who pass the SFRE are then slotted to try out in the Special Forces Assessment and Selection (SFAS) alongside every other Green Beret hopeful. SFRE graduates are significant more likely to don the Green Beret.