> you can't take a signing bonus then not show up for work.

You can if your union goes on strike between you getting your signing bonus and your start date. Striking is not the same as quitting in the eyes of the law.

Striking is not the same as quitting. If negotiations were ratified next week, workers would return and could not face retaliation in benefits or pay for striking. The university could withhold pay for missed shifts during the strike and potentially clawback a prorated portion of the remission at best, but clawing back remissions in their entirety and charging late fees for not paying by a deadline is bad faith and won't be looked upon fondly by the NRLB. While the decision will likely end up being made by a court, to me this definitely seems like illegal retaliation and not a case of students biting off more than they could chew.

If you are part of a strike, then yes, actually, you are legally protected against some forms of retaliation, including possibly this form. We'll see how it plays out in court, but it is by no means as simple as you're laying out. This is not "people decided to not show up for work," it's a collective bargaining action against a very clearly hostile employer.

If they had already been paid out, yes. Company bought you a $10k car in January, you strike in March. The company isn’t allowed to retroactively “unbuy” the car and declare that you now owe them $10k. Even if the condition for keeping the car was a full year’s employment you can’t take it — striking isn’t legally quitting.

Even stronger, if employees usually get an annual bonus but the year of the strike they don’t you might get bitten for retaliation.

I feel like yes, you would get options in your contract. But it doesn’t matter. The legality of this isn’t why it’s stupid. It’s the immense bad will from a class of poor students that are already doing a ton of work for very little. They would effectively now be asking students to pay to work.

Organized labor is coming for grad students.

If you had been issued options to buy shares that had already vested it'd be pretty insane for a company to try and claw those back. Pausing the vesting schedule might be a bit more understandable but is honestly pretty damn petty for what you're getting unless the strike lasted a good chunk of the year.