Many expect legally-recognized same-sex marriage (SSM) to have significant effects on people’s behavior. This stance regarding SSM’s effects reflects a persistent, wide-spread belief that the law has a significant and reliable effect on social norms. However, I will argue that belief in the law’s capacity to effectively change social norms does not adequately take account of the nature of social norms, how they actually change, and the limits of government intervention. Through examining SSM and these factors more closely, I cast doubt on the claim that the law significantly, reliably, and effectively challenges mainstream, marital social norms. Instead, SSM is better seen as an indicator of gradual changes in conceptions of marriage. When explaining changes in marital social norms, we should not waste our time on SSM, rather we should look to non-state factors.