Giants Pitcher Sergio Romo -- Won't Be Prosecuted In Vegas Airport Bust

San Francisco Giants pitcher Sergio Romo (and his beard) can breathe a sigh of relief ... 'cause the world series superstar will NOT be charged following his recent Vegas bust, TMZ has learned.

We broke the story ... Romo and his beard were detained by cops on New Year's Day -- after he allegedly became "angry and aggressive" with a TSA agent at the airport. According to sources, he appeared to be under the influence.

Romo and his beard were cited with a misdemeanor -- and escorted off airport grounds.

A rep for the Clark County District Attorney's office tells us ... Romo will NOT be charged due to a "lack of prosecutorial resources."

The rep explains, "We simply do not have the manpower or resources to go forward on every case ... and must weigh the value, provability, and seriousness of each case accordingly."