An attorney for a union challenging Indiana's new right-to-work law said Wednesday that he's perplexed by the state's court filing opposing his amended complaint in which he argued the law is unconstitutional.

Dale Pierson, who's representing International Union of Operating Engineers Local 150, defended his complaint and said his purpose for filing it was to add arguments not included in the original complaint. Pierson said he didn't understand why the first three pages of the state's eight-page filing Tuesday focused on the claims and relief sought by the union being the same as those in the original lawsuit filed Feb. 22.

"Our motion is designed to add two counts. It's not designed to change anything in the first 10 counts of the complaint," he said.

One of the additional charges from the union is that the right-to-work law violates the 13th Amendment, which outlawed slavery and involuntary servitude. The union also is challenging how the state defines an employee.

The union contends federal law requires it to represent everyone in the bargaining unit and that it is unconstitutional for a state to say it cannot collect for the cost of its services.

"We think the way that the 13th Amendment has been interpreted it is broad enough to cover that concept, that you can't force us to represent people and then take away our ability to be compensated for those services," Pierson said.

The state contends the argument does not apply and that the right-to-work law does not compel the union to provide services to anybody.

As for the employee definition argument, the union contends the state Department of Labor adopted an emergency rule in March that includes a definition of employee to include job applicants. Pierson said this would extend the prohibition against union security clauses to job applicants.

The state contends the emergency rule expires June 13, which could come after the court rules, and that there is no indication it has been used, so the argument should be dismissed. Pierson said the union shouldn't have to wait for a violation to occur to argue the point.

Pierson said the union will file its formal response to the state's opposition by the May 11 deadline.