Two recent Australian cases raise important questions about sex and gender identity as legal categories. One, a decision of the highest appellate court in NSW, held that a change in sex under the law of a State does not require a change to be made in a marriage certificate issued under Commonwealth law. The other is a decision still awaiting a final hearing in the Federal Court, where the operator of a females-only only social networking site is being sued for her decision to exclude an applicant who was born biologically male but has since undergone “gender affirming surgery”. Though neither case explicitly involves anyone whose views are based on religious beliefs, both raise important issues which connect with “law and religion” interests, and are worthy of noting.