Former Gov. Jon Corzine had allowed the unions to trade the day after Thanksgiving for Lincoln's Birthday in February.
The workers can take the time as a vacation day.
Communications Workers of America state director Hetty Rosenstein told Gannett New Jersey's Statehouse Bureau "it's dirty pool."
Employee Relations director David Cohen says legislation is needed to exchange holidays. Otherwise, Cohen says state workers could get both days off.
One union leader is threatening to go to court to enforce Corzine's 2009 Memorandum of Agreement.
State workers receive 13 holidays off.