This article compares the U.S. Defense of Marriage Act and the Australian Marriage Amendment Act of 2004, both of which define marriage as between one man and one woman, and prohibit benefits to same-sex partners at the federal level. The author then goes on to consider the ramifications of unsuccessful court challenges to both laws. In the U.S., she finds that the consequences would not be that great because the federal government has limited ability to regulate marriage, hence the states would still be able to allow same-sex marriage. In Australia, in contrast, she believes that an unsuccessful court challenge (i.e., where the Australian Supreme Court upheld the validity of the Marriage Amendment Act) might also be held to preclude the states from allowing same-sex marriage as well because the Australian federal government has more Constitutional authority to regulate marriage than is the case in the United States.