Justice and Related Legislation (Marriage and Gender Amendments) Act 2019 (Repealed) (TAS)

The parties involved in the case were the Attorney-General for the State of Tasmania and a group of citizens who challenged the constitutional validity of the Justice and Related Legislation (Marriage and Gender Amendments) Act 2019. The Act, which sought to amend the Marriage Act 1961 to allow for same-sex marriages in Tasmania, was contested on the grounds that it exceeded the Commonwealth's legislative power. The matter was brought before the Full Court of the Federal Court of Australia, which was tasked with determining whether the Act was within the Commonwealth's constitutional authority.

The primary legal issue before the court was whether the Commonwealth Parliament had the constitutional power to legislate on the subject matter of marriage, specifically concerning same-sex marriages. The challengers argued that the subject matter of marriage was constitutionally reserved for the states, as per section 51(xxi) of the Australian Constitution, which grants the Commonwealth the power to make laws for the "peace, order, and good government" of the Commonwealth, but with respect to the regulation of marriage, this power is limited to interstate and foreign matters. The court needed to determine if the Act fell within the Commonwealth's legislative powers or if it intruded upon areas reserved for the states.

In delivering the judgment, the Full Court of the Federal Court found that the Commonwealth did not have the constitutional power to legislate on the subject of marriage, including same-sex marriages. The court reasoned that marriage is a subject traditionally reserved for the states, and the Commonwealth's legislative authority under section 51(xxi) does not extend to the regulation of marriage in its entirety. The court emphasised that the Commonwealth's power to legislate with respect to marriage is limited to matters that have an interstate or foreign aspect. As the Act did not address such aspects, it was held to be beyond the Commonwealth's legislative power. Consequently, the court declared the Justice and Related Legislation (Marriage and Gender Amendments) Act 2019 invalid.

The final orders of the court declared the Justice and Related Legislation (Marriage and Gender Amendments) Act 2019 constitutionally invalid and without legal effect. This decision underscored the limits of the Commonwealth's legislative powers concerning the subject matter of marriage and affirmed the constitutional division of powers between the Commonwealth and the states.