I work in Massachusetts, my employer being in New Hampshire.
Is my employer required to pay me time and a half for working on Federal Holidays?

I've been previously paid in the past for Federal Holidays and noticed I didn't get paid anything extra for working on Memorial Day.
They never informed me of any changes, just didn't pay me for time and a half. Is this legal?
I also noticed they hadn't paid me for Martin Luther King's Birthday back in January as well.

A fellow employee stated that he wasn't paid for New Years also and no one else in the company had been notified (as far as I know) about not paying us for any Federal Holidays anymore.

I didn't know where to post this. My apologies if in the wrong place.