Can Your Employer Force You To Sign A Contract Saying You Volunteered To Work On Sunday?

It's been awhile since I answered my reader questions here. This question is one I found interesting:

I have a question about unfair work practices. My husband works for a very large company that does extremely high volume during the Christmas season. All employees were required to work on Sunday (following a six day work week). They were told that everyone was expected to be there despite the fact that no one had a day off during the week. This morning when they arrived, they were told that they had to sign a document that said they had volunteered to work on Sunday, otherwise they would be sent home. Most of them signed because they were already there and had planned on working today. Are companies allowed to do something like this?

I can read this question three different ways, so I'll address them all. 

Agreement to volunteer to work for free: The first way I read it is whether your employer can make you sign an agreement that you are a volunteer so as to avoid paying you. The answer is a flat-out no. An agreement that tries to waive your right to overtime or to be paid for all hours worked under the Fair Labor Standards Act is not enforceable. Furthermore, if you work for a for-profit company, you are never a "volunteer" such that you can agree to work for no pay. If the employer suffers or permits you to work, then you are entitled to pay.

Agreement to waive religious accommodation: If you have requested a religious accommodation to work on Sunday, then the EEOC and courts would refuse to enforce an agreement waiving future discrimination. In other words, you can't be forced to sign an agreement to be discriminated against in the future. On the other hand, where states like Florida allow employees to be required to sign agreements in consideration of continued employment, if the employer handed you an agreement on Monday that said you were agreeing that you waived your right to sue for religious discrimination because you worked voluntarily on Sunday, would that stand? The truth is, maybe. The courts have been very harsh on employees regarding noncompete agreements and arbitration agreements that are presented as "sign or be fired," so would a "sign or be fired" release fly? I think probably not, but I'd never underestimate the ability of employers to push for case law that grinds employees' rights into dust. Allowing a waiver like that immediately after an act of discrimination for the sole consideration of continued employment would make a mockery of the employment discrimination laws. If an employer presents you with an agreement saying sign a waiver of discrimination that just happened or be fired, I think that would be unlawful retaliation and discrimination.

Agreement to work on Sunday: If the agreement simply says that you agree to work on Sunday, and you don't have any need for a religious accommodation, then your employer can make you sign an agreement to work on Sundays, and they can say you voluntarily agreed to work on Sundays. Which I guess is true, if they mean you "voluntarily," under threat of losing your job, decided to sign. If you live in one of those states like Florida that doesn't consider "sign or be fired" to be economic duress, then they can probably make you agree.