Green’s Dictionary of Slang

(US) a former convict.

1993		L. Rodríguez Always Running (1996) 114: He was a vetenaro, just out of YTS. Along with a handful of other pintos.
1997		R. Barcena Introduction to Sánchez Loves of Ricardo 🌐 Perhaps associating him with his pinto (convict) background, his fellow professors felt that he was too harsh and unrefined.