A Kansas sheriff’s jail policy allowing inmates to receive and send only postcards through the mail violates the free speech and due process rights of prisoners and their families, civil rights advocates said in a lawsuit filed Thursday.

The American Civil Liberties Union and the Social Justice Law Collective are seeking a court order to end the practice. Their lawsuit, which seeks class-action status, was filed in federal court against Wilson County Sheriff Pete Figgins.

“These policies create a huge problem for inmates and their loved ones because they don’t allow enough space to correspond about anything meaningful, and postcards are open to be read by anybody as they pass through the postal system,” said Doug Bonney, legal director of the ACLU Foundation of Kansas.

The Wilson County jail in southeast Kansas forbids inmates and those who correspond with them from sending letters in envelopes, and requires all correspondence to be on prepaid postcards. The only exception is legal mail, such as letters from an attorney’s office.

Figgins said some people have used coded language, or planted a letter in sealed envelopes that are meant for someone they’re not supposed to have contact with.

“A lot of it is for security reasons,” the sheriff said. “We want to know what is being said.”

The civil rights groups say the policy infringes on the constitutional rights of the inmates and others to express themselves fully, and exposes to others sensitive or private matters such as medical, financial, spiritual or intimate information. It also violates due process rights, the groups say, because those whose letters have been confiscated are not told or given an opportunity to protest that decision.

Because telephone calls from the jail are expensive and family members often live too far away to regularly visit, communication by mail is often the only practical form of communication, the groups argued.

Postcard-only policies began to spread across the country in the years after Arizona Sheriff Joe Arpaio, known for his hardline stance on illegal immigration, instituted one in his Maricopa County jail, Bonney said. Most have been successfully challenged in the courts. Similar policies have been overturned in Florida, Colorado and several other states, said SJLC attorney Joshua Glickman.

The ACLU reviewed jail mail policies in 2013 and found about 10 with postcard-only policies in Kansas, Bonney said. All but Wyandotte County rescinded their policies after receiving a letter from the ACLU. The ACLU sued Wyandotte, and the county agreed in an out-of-court settlement last year to change its policy.

But Wilson County never responded to the original open records request, and their policy went unnoticed until the ACLU began receiving complaints last fall from people at the jail. Bonney said he sent the sheriff a letter explaining why the policy was unconstitutional, but never got a response.

Figgins said he often gets letters and emails from organizations that think they can do a better job of running his jail or patrol.

“We run it because this is what we are experienced in,” Figgins said. “We know how to run a correctional facility.”