Five law graduates from the University of Indonesia argue part of the country's Marriage Act is unconstitutional.
They have said the Constitution protects religious freedom and the rights for all people to be treated equally under the law.
According to the claim filed in the Constitutional Court, the group wants Article 2.1 of the Act struck out, saying it "forces people to conduct a marriage according to each party's religious law".
In practice, that means people of different faiths cannot hold a marriage ceremony unless one person changes religion.
The law graduates argue the Act "limits the people's rights to marry" and "diminishes the principle of equality".