Several noted legal scholars, most prominently Richard Posner, have applied the economic analysis of law to the debate over same-sex marriage. In this note, I argue that the economic approach to law is ill-equipped to deal with the issues of principle, dignity and rights that are at the core of the debate, regardless of the position taken on the issue. Other scholars, such as Darren Bush, acknowledge the shortcomings of the economic approach, such as the importance of the assumptions on which cost-benefit analysis is made, but they do not appreciate that this is symptomatic of the economic approach as a whole, not merely the application of it by some scholars in some cases. My contention is that the economic approach to law is appropriate regarding issues of policy, where trade-offs are essential and necessary, but not regarding issues of principle, with which trade-offs are not so easily made.