A Hawaii convict serving his sentence in a private prison in Arizona is suing the state Department of Public Safety over its policy requiring all mail to and from inmates to be written in English.

The Native Hawaiian Legal Corp. filed a lawsuit against DPS and Department Director Nolan Espinda in state court Thursday on behalf of Arthur Vinhaca.

Vinhaca is serving a 40-year prison term for multiple counts of sexual assault.

The lawsuit claims that DPS’ English-only mail policy prohibits prisoners from receiving letters written in Hawaiian and unduly burdens communications between families and their loved ones behind bars.

The policy requires the department to make accommodations for inmates who are unable to write in English or if the recipient does not read English.

Vinhaca claims he is of Native Hawaiian descent, that his parents were fluent in the Hawaiian language and that his family continues to communicate with each other in Hawaiian.

English and Hawaiian are the state’s official languages.

The lawsuit claims that prison officials censor or confiscate all mail written in Hawaiian sent to prisoners at all state prisons and jails.

Vinhaca is serving his time in Saguaro Correctional Center, a private prison run by Tennessee-based Corrections Corp. of America, under contract with the state.

A DPS official said the department has been advised not to comment on the lawsuit.