My name is ***** ***** I'd be happy to answer your questions today.
It's not lawful. An employer may not penalize an employee for taking FMLA leave - and that also means they cannot make you work an alternate day instead. If they fire you for refusing to work on a Sunday after you took FMLA, you could sue for reinstatement, back pay, and your attorney's fees. You should be aware, though, as a practical matter, that it could be many months before you get any money from your employer, so keep that in mind when deciding on a course of action.
Your other option is to report them to the labor board again and ask them to investigate and impose penalties for a recurring violation of the law. If they'd given you more notice, you could have a local attorney contact them on your behalf, via phone or letter, but you might have trouble finding someone on a Saturday. Consider if you want to spend a few hours looking for a local employment attorney who works on the weekend. Or you could talk to a manager or HR employee yourself, explain that their actions are in violation of the law, and let them know you'll be reporting them to the labor board and filing a lawsuit if they either force you to work on Sunday or take negative action against you because you refuse to do so.
If you have a sincere religious objection to working on a Sunday, you can note that as well, because they're required to make reasonable accommodations for that and it would be discrimination
to make you work in violation of your religious beliefs or to fire you for refusing to work.
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