Many people, on both sides of the issue, believe that understanding how sexual orientations develop is legally, ethically, and politically relevant to LGB rights. This article examines two “arguments from etiology,” which the author calls the “born that way” and the “not a choice” arguments, ultimately concluding that how sexual orientations develop is neither relevant nor useful in legal, political, or social contexts. These arguments connect to the role of the “immutability factor” in the context of the Equal Protection Clause of the 14th Amendment to the U.S. Constitution and in similar clauses in state constitutions. The article begins with a review of the conceptual landscape related to sexual orientation and immutability. Setting aside the strength of their empirical premises, some ethical and pragmatic criticisms of these etiological arguments are then discussed. Finally, the article examines how immutability has been discussed in recent court cases about same-sex marriage. In these cases, courts are divided on the meaning of immutability, its relevance, and how to determine whether sexual orientations are immutable. The article concludes that rather than focusing on scientific issues about how sexual orientations are embodied, the better strategy for LGB advocates is to focus on arguments based in justice, equality, and fairness.