The ACLU has filed a federal lawsuit arguing that an Arizona law requiring all state contractors to certify that they aren’t boycotting Israel violates the First Amendment.

The law, enacted in March 2016, requires that any company that contracts with the state submit a written certification that it is not currently boycotting Israel. The ACLU filed the case on behalf of an attorney and his one-person law office, which contracts with the government to provide legal services to incarcerated individuals.

The Supreme Court ruled decades ago that political boycotts are protected by the First Amendment, and other decisions have established that the government may not require individuals to sign a certification regarding their political expression in order to obtain employment, contracts, or other benefits.

The ACLU represents attorney Mikkel Jordahl, who has had a state contract to provide legal advice to inmates in Coconino County Jail for 12 years. Because of his political views, Jordahl refuses to purchase consumer goods and services offered by companies operating in Israeli settlements in the occupied Palestinian territories.

Jordahl wants to extend his boycott to his solely owned law firm, Mikkel (Mik) Jordahl P.C. He also wants to use his law firm to provide legal support to other organizations engaged in boycotts and related political expression, but the law’s certification requirement prevents state contractors such as Jordahl’s firm from participating in these activities.

Jordahl’s firm must renew its contract with the county every year. When he got the renewal paperwork in October 2016, it included an extra form that he had to sign to certify that the firm “is not currently engaged in a boycott of Israel.” Jordahl signed it under protest, and has made sure to separate his personal boycott from his firm’s activities. Now, in order to renew his contract, Jordahl has again been asked to sign the certification. If he agrees, Jordahl will have to limit his boycott participation. If he refuses, he will put a great deal of his income at risk.

The lawsuit argues that the Arizona law violates the First Amendment for several reasons: it compels speech regarding protected political beliefs, associations, and expression; restricts the political expression and association of government contractors; and discriminates against protected expression based on its content and viewpoint. The lawsuit asks the court to strike down the law and bar state officials from requiring contractors to certify that they are not participating in boycotts of Israel.

The case is currently on appeal to the U.S. Court of Appeals for the Ninth Circuit.