Historically in English, the masculine form was the default gender-neutral term. "Mankind" to refer to all humans. "All men are created equal" to refer to all

Historically in English, the masculine form was the default gender-neutral term. "Mankind" to refer to all humans. "All men are created equal" to refer to all humans. "No one shall be arbitrarily deprived of his nationality nor denied the right to change his nationality" refers to all humans. More recently as other comments have pointed out, singular "they/their" has become more accepted. "No one shall be arbitrarily deprived of their nationality nor denied the right to change their nationality".