In 2009, Laura Langbein and Mark Yost published an empirical paper on same-sex marriage, and they concluded: “The argument that same-sex marriage poses a negative externality on society cannot be rationally held.” Here we provide a multifaceted critique. We argue that their empirical strategy is unable to test a realistic externality mechanism. Furthermore, we show that the data they use for their test is inappropriate and that the actual results found are based on questionable coding of their legal variables. Still further, their results are often not robust to alternative estimation methods and universally lack statistical power. The conclusion drawn in their paper, that there can be no rational grounds for opposing same-sex marriage laws, is not supported.