The International Union of Operating Engineers Local 150 has filed suit saying the newly passed right-to-work legislation is illegal.
Unions are trying to minimize the effects of the legislation before the deadline.
The passage of right-to-work was the big news this week at the statehouse, but the legislature also passed some other prominent bills.
Bill passes 28-22 and now awaits Governor Daniels' signature.
Democrats boycotted a right-to-work hearing Monday in the Senate as a sign of protest.
The major news out of the statehouse this week was the passage of right-to-work in the Indiana House of Representatives.
The House voted to pass right-to-work legislation with a 55 to 42 vote.
Indiana House Democrats did not show to the session Tuesday.
The House considered several amendments to the right-to-work bill Monday.
More than four dozen amendments to the House version of right to work could be debated Monday.