Two years after the Nato-backed uprising, which ousted Muammar Gaddafi, Libya is still in messy transition with no new constitution and its temporary assembly caught in deadlock between an Islamist party and political rivals.
As in Tunisia and Egypt, where autocratic leaders were ousted in the Arab Spring revolts, Libya has seen fierce debate over the role of Islam in its new democracy.
The immediate scope of the General National Congress's decision was not clear, but a special committee would review all existing laws to guarantee they comply with Islamic law.
"Islamic law is the source of legislation in Libya," the GNC said in a statement after the vote. "All state institutions need to comply with this." The Muslim Brotherhood's Justice and Construction party is one of the most well-organised forces in Libya.