The appeal, made this week to the official Human Rights Commission, lists the detention since February 2007 of nine political activists, the arrest in May of well-known reformer Matruk al-Faleh and Interior Ministry bans on travel abroad that prevent blacklisted Saudis from leaving the country for years.
"The government provides you with the power …to monitor and ensure that governmental institutions abide by the law," said a statement delivered to the commission and sent to Reuters on Wednesday in the name of 38 public figures, including some former detainees who are prevented from foreign travel.
The statement also referred to hundreds of "forgotten ones" who languish in Saudi jails without trial.
"Illegal arrests persist against Saudi citizens, especially against those who express their opinions in peaceful and civilised ways … the detainees are entitled to a fair trial, which Saudi law grants them," it said.
There was no immediate comment by Saudi officials on the appeal.
The Interior Ministry has detained several thousand people since al Qaeda-allied militants launched a campaign of violence to destabilise the U.S.-allied government in 2003.
Rights groups say the state’s counter-insurgency strategy has been abused to crack down on peaceful calls for the ruling Al Saud family to transform the country, the world’s biggest oil exporter, into a constitutional monarchy.
Western diplomats say many Saudi royals and their supporters fear losing their privileges and that radical Islamists could win if elections were held to the Shura Council, an advisory body appointed by the king.
Powerful Muslim clerics are already given wide control over society, through controlling education, the judiciary and a law enforcement body charged with maintaining public morals.