The director of the government watchdog group Citizens Union is off the hook for a drug possession charge leveled against him in October.

Dick Dadey showed up at his arraignment in Brooklyn with proof that he has completed a drug rehab program since he was arrested, a law enforcement source said Friday, and a judge dismissed the misdemeanor charge.

The charge could technically have landed him in jail for a year but that sentence is rarely enforced, the source said.

Cops found small quantities of crystal meth and ecstasy in Dadey’s Brooklyn Heights home in September, a source told the Post at the time.

“I accept full responsibility for the mistake I made and apologize without condition to those who placed their trust in me and who I failed,” Dadey said in a statement posted to Twitter.

Citizens Union was founded in 1897 to combat corruption in New York City and State government.

Dadey, the group’s Executive Director, took a leave of absence on Sept. 20.