Can an employer use FMLA against you when choosing your days off and the shift you wo

I work for a company that has over 150 supervisors and is open 24 hours a day every day, which has 3 shifts. They just adjusted everybody's days off and shift they work and they did it based on hours worked. Therefor if you were out on LOA or for an FMLA approved illness they are using the time you weren't there against you. Which means I'm going from the best shift that I've had for 10 years now to the worst. Can they do that?

This may or may not be legal depending on EXACTLY how the policy is worded and applied.

If the company goes SOLELY by hours WORKED and does not count ANY kind of leave, including paid leaves and including vacation or paid sick time, then it is probably legal.

If the company picks and chooses which kinds of leave do or do not count as hours worked, then it is probably illegal.

They are not using vacation against us. Only attendance, sick days, LOA and FMLA. They're basically saying that we can take a medical leave or use FMLA but if we do we can lose our days off and may have to go a different shift...not in so many words of course.

I would still hesitate to declare it positively legal or illegal, though I'd be a lot more comfortable about the legality if vacation were included. While you cannot be 'punished' for using FMLA, at the same time the law never intended for employees on FMLA to get privileges that employees on non-FMLA leave are ineligible for. I would run this one past the US DOL.