I work for a church in Maryland and was allowed to carry 45 days of vacation and accure sick leave. The board decided to change policy and do away with sick leave and only allow employees to carry a maximum of 25 days of vacation. The decision was immediate and they stated all time must be used by the end of the year (which it is the end of the year almost) and if not used will be lost. Also they changed our 8 paid holidays to 3 a year and Thanksgiving is not one of them. I know MD is not the best labor law state, but is an employer allowed to take away your leave and not pay you for it?

Except in the states where vacation time is considered wages (and Maryland is not one of them) yes, they are. It may not be fair, but it is legal.