Libyan National Party Secretary-General Fathi Sager and Policy Manager Ali Tekbali are facing the death penalty for allegedly insulting Islam with political propaganda displayed during 2012 elections for the General National Congress.
Human Rights Watch said they were charged this week in Tripoli with religious crimes and for "instigating division" when they displayed posters seen as insulting the Islamic Prophet Mohammed.
A series of U.N. reports this week said Libya is lagging in democratic reforms in part because of the enduring legacy of former leader Moammar Gadhafi, who died after falling into rebel hands in 2011.
Libya has enacted some democratic reforms since the civil war ended in 2011 though internal rivalries are aggravating ongoing security challenges.
Deputy Director of Middle East Programs for Human Rights Watch Joe Stork said political speech should be respected in a democratic Libya. Judicial authorities should drop the charges, he said.
"Authorities should be abolishing draconian legislation, not using it as a tool to cut off free speech," he said in a statement Thursday.