WICHITA, Kan. (AP) — Civil rights advocates are suing the Wilson County sheriff over his jail’s policy of allowing inmates to receive and send only postcards in the mail.

The American Civil Liberties Union and the Social Justice Law Collective contend the policy violates the free speech and due process rights of prisoners and the people who write to them.

Their class-action lawsuit, filed Thursday in U.S. District Court of Kansas, seeks a court order that puts an end to the practice.

Wilson County Sheriff Pete Figgins says the mail policy was put in place for security reasons to know what is being said in them.

ACLU lawyer Doug Bonney says these policies create a huge problem for inmates and their loved ones because they don’t allow enough space to correspond about anything meaningful.