PLEASE tell your boyfriend to fight this. The fact that he's being written up now is a sign that he's being badgered and harrassed, and he has a record of the meeting with the union rep, even if the rep wasn't supportive at the time.

I had excrutiating problems with my last boss, who was also trying to look for an excuse to sack me ... it was the hardest thing I've ever had to do (triggered a psychotic break in the end) but I got an out of court settlement of 5000 pounds, and all my outstanding holiday pay, over time, and notice (though I hadn't been able to give notice.)

It's worth his sticking to his guns, you don't want him to be let go with a bad reference, and without his severence pay.

My advice, he's in a fight, whether he likes it or not. If he hangs tough, the employer will have to pay. I don't know how your tribunal system works in the US, but here in the UK it really worked for me.