Players associations of the National Hockey League (NHL), Major League Baseball (MLB) and National Football League (NFL) filed suit against the city of Pittsburgh Tuesday, claiming that a tax imposed on athletes in the city is in violation of both the Pennsylvania and US Constitutions.

The suit also lists three athletes as plaintiffs, including former MLB player Jeffrey Francoeur, NHL player Kyle Palmieri and former Pittsburgh Penguin and NHL player Scott Wilson. The players listed have all competed in Pittsburgh, whether as members of Pittsburgh sports or as a member of a visiting team, and are non-residents, making them subject to the tax.

The city of Pittsburgh taxes income earned by professional athletes at venues in the city at a higher rate than any other income at any other location in the city. There is one group that is exempt from tax: athletes that live in Pittsburgh.

The Pennsylvania Constitution states that all taxes must be uniform. Pittsburgh cannot tax non-residents more than it taxes residents, and it cannot “single out a class of employees, like professional athletes, for a higher rate of taxation.” The plaintiffs state that the tax the city has imposed is in direct violation of this rule, as well as a rule in the US Constitution, which prohibits “states and municipalities from establishing conditions on professional work that are more burdensome for nonresidents than they are for residents.”