More trouble for Cowboys star Randy Gregory ... the defensive lineman has been suspended indefinitely after violating the league's substance abuse policy, the team announced Tuesday.
Gregory -- who has been punished multiple times since he was drafted in 2015 -- was conditionally reinstated back into the league last July after a year-long suspension.
But the Cowboys say Gregory violated the terms of his reinstatement ... and the league has kicked him to the curb yet again.
Gregory's drug issues started even before he was drafted by the Cowboys ... he was popped for marijuana at the 2015 Scouting Combine.