KANSAS CITY, Mo. (AP) — The American Civil Liberties Union of Missouri and two state library associations are suing over a new state law that bans sexually explicit material from schools, saying it violates the rights of librarians and students.

The lawsuit filed Thursday contends that the Republican-backed law, which took effect in August, has caused Missouri school districts to remove hundreds of books from their shelves.

The ACLU, the Missouri Association of School Librarians and the Missouri Library Association are asking the Circuit Court in Kansas City to find the law unconstitutional or clarify how and when it applies.

The law was passed as challenges to the content of library books — both in schools and public libraries — have increased across the country over the last two years.

Missouri’s Republican secretary of state, Jay Ashcroft, has proposed a rule that would block public funding for libraries that make “inappropriate” books available to minors. The proposal has been widely condemned by librarians and free speech advocates.

In the latest lawsuit, the ACLU sued Jean Peters Baker in her role as the Jackson County prosecutor and on behalf of all county prosecutors in Missouri.

Michael Mansur, a spokesman for Baker’s office, said Friday that they had not seen the lawsuit and couldn’t comment.

Librarians and other school officials face up to a year in jail or a $2,000 fine for violating the policy, which makes it a crime to provide minors with sexually explicit visual material. Exceptions are provided for works of art, science classes and other educational courses.

The lawsuit also contends that librarians and others could violate the law regardless of whether the material is provided inside or outside of a school building or school hours.

As of November, about 300 titles had been banned from school libraries across the state, according to the lawsuit. Many of those books were written by or about minority or LGBTQ individuals, but they also include graphic novels, human anatomy books and Holocaust history books.

The law endangers not only school librarians but public and academic librarians who work with K-12 schools, Joe Kohlburn of the Missouri Library Association’s Intellectual Freedom Committee said in a statement.

“Librarians have been undermined politically in this state for long enough, and the fear of prosecution is an ongoing issue for keeping qualified professionals in Missouri, as well as bringing new people into the profession,” he said.

The ACLU argues that the law violates educators’ due process rights because it is unconstitutionally vague and allows government overreach. It also argues that the suit violates students’ First Amendment rights.

The lawsuit notes that federal and state law already prohibits providing obscene and pornographic materials to minors, and that school boards approve procedures for choosing appropriate library materials.

“Extreme politicians in Jefferson City are using the government-knows-best model for legislation — in this case telling parents what their children can and can’t read at school and, in some cases, at home, while imposing criminal penalties on those who might disagree,” said Gillian Wilcox, deputy director for litigation for the ACLU of Missouri.

Melissa Corey, president of the Missouri Association of School Librarians, said one of the group’s major concerns is not only removing books currently on the shelves, but the potential for “a chilling effect” on what books are purchased in the future.