A federal judge in Denver is considering whether the U.S. government should require people to pick a gender to get a passport.

The issue emerged through a lawsuit filed by a Colorado resident who was denied a passport for refusing to check "male" or "female" on the application. A judge is set to hear arguments Wednesday.

Lambda Legal sued last year on behalf of Dana Zzyym of Fort Collins, who was born with ambiguous sex characteristics. The lawsuit claims that requiring people to check a box marked either "M'" or "F'' is discriminatory and asks people like Zzyym to lie.

Countries including Australia, New Zealand and Nepal allow people to have their gender marked as "X'' or "other" on passports.