The letter nonbinary people, who see themselves as neither male nor female, want to use on identification documents like their birth certificate or passport to reflect their genderβpreventing them to do so would force them to lie about their true identity.
Although a number of countries allow their citizens to use X and O (for βothersβ), rather than M or F, on their passport to identify themselves, however, the odds of their being denied entry by border control authorities elsewhere are neverzero.