'127 Hours' Amputee Aron Ralston Helps GF Escape Long Arm of the Law

2/20/2014 12:30 AM PST

Aron Ralston -- the guy who cut off his own arm to free himself from a boulder -- just helped free his girlfriend, too -- from criminal charges.

TMZ broke the story ... Ralston -- the real-life inspiration for the movie, "127 Hours" -- and his GF Vita Shannon were arrested last December in Denver for allegedly assaulting each other during an ugly argument. 

Charges against Ralston were quickly dropped -- lack of evidence -- but authorities went after Shannon ... for allegedly punching the one-armed man in the back of the head.

Shannon was in court Wednesday ... and Ralston didn't show up to testify  ... so prosecutors dropped the charges.