JEFFERSON CITY, Mo. (AP) — Public employee unions are seeking to block a new Missouri law imposing restrictions on how they operate.

The lawsuit filed in St. Louis County seeks an injunction against a law set to take effect Tuesday that was enacted by former Gov. Eric Greitens and the Republican-led Legislature.

The law requires some public employee labor unions to hold an election every three years on whether workers want to continue their representation. It also requires those unions to get annual permission to deduct dues from workers’ paychecks.

The lawsuit claims the measure violates Missouri’s constitutional right for employers to organize and engage in collective bargaining. It also claims the law is discriminatory because it affects some public employee unions while exempting others.