Unfortunately it wasn't anywhere in writing. My manager verbally said I would only need to work maybe 1 or 2 overnight shifts a year, but I have worked numerous, then expected to come in for evening shift. This has resulted in migraines and vomiting, which I wasn't even allowed to leave for. I knew it would be every other weekend, but didn't know how awful the scheduling would be.

Its not really illegal, just inconsiderate.