It's one thing for Jay Leno to be mocked endlessly by rival David Letterman for moving to an earlier timeslot. Far more insulting: Being branded a scab by his own union .

The Writers Guild of America has initiated disciplinary proceedings against Leno, Variety reports, and could ultimately expel or suspend his union membership. The union is upset that Leno wrote his own material in January 1008, in the weeks before the writers strike ended, allowing the Tonight Show to return to the air and compete against David Letterman, who owned his Late Show outright and was thus able to settle with the union early. Had Leno not come back, Letterman almost certainly would have clobbered him in the ratings.

NBC said at the time the union gave Leno permission to write his own material in a meeting and that the union's prior contract allowed him to do so anyway.

What ramifications a union expulsion or suspension would have for Leno's new 10 pm show are unclear. But it would definitely be embarrassing for the late-night host to be slapped by the union he publicly supported in a big way during the writers strike last fall. Sounds like the union isn't too happy with Leno annexing a huge chunk of NBC's prime time. At least the time didn't go to reality shows, guys. Those programs barely even have writers.