A federal judge in Louisiana on Tuesday blocked a state law requiring the display of the Ten Commandments in every public school classroom. The legislation, which was passed by state lawmakers this year, has been closely watched since Louisiana is the first state to enact this kind of mandate in more than 40 years.

The decision was a setback for supporters of the measure, but not an unexpected one: Proponents of the measure have braced themselves for backlash and, in many ways, have invited a lengthy legal fight as part of a larger effort by conservative Christian groups to amplify public expressions of faith.

John W. deGravelles, a U.S District Court judge who was appointed to the bench by President Barack Obama, found that the law, which was set to take effect on Jan. 1, was unconstitutional. He forbade the state from enforcing it.

In his decision, Judge deGravelles wrote that the law was “coercive to students, and, for all practical purposes, they cannot opt out of viewing the Ten Commandments when they are displayed in every classroom, every day of the year, every year of their education.”

He added: “There are any number of ways that the state could advance an alleged interest in educating students about the Ten Commandments that would be less burdensome.”

Attorney General Liz Murrill of Louisiana, a Republican, said in a statement she strongly disagreed with the decision and vowed an immediate appeal. Supporters of the bill expect a friendlier reception from the U.S. Court of Appeals for the Fifth Circuit, which is considered one of the nation’s most conservative courts.