GOP presidential candidate Sen. Rand Paul returned from New Hampshire to Washington D.C. so he could vote Monday evening for a resolution calling for the release of American citizens who are wrongfully imprisoned in Iran.

Four men are included under the resolution, which calls for their immediate release. All four men have been detained in Iran for several years, the longest detention being since 2007.

Saeed Abedini is from Idaho and is a Christian pastor. He has been wrongfully imprisoned in Iran since 2012, after being sentenced to eight years on charges related to his Christian religious beliefs.

Amir Hekmati is from Michigan and is a former United States Marine. He has been unjustly detained since 2011 when he went to visit his Iranian relatives. He was sentenced to 10 years for espionage.

Jason Rezaian is a reporter for the Washington Post and credentialed by the Iranian Government. He was imprisoned in 2014 without a trial.

Robert Levinson is an FBI official who disappeared in Iran in 2007. According to Paul’s press release, “He is the longest held United States citizen in United States history.”

Paul believes the nation’s diplomats should make it a primary goal to ensure these men return home.

“I’m horrified by the wrongful imprisonment of the four American prisoners in Iran and the increasingly dire reports of human rights violations against ethnic and religious minorities and political dissidents in Iran,” said Paul. “Their suffering is a collective stain on the conscience of every lover of liberty, and we must fight for their safe return to their homes and families.”