Welfarist law and economics ignores the distributive consequences of legal rules to focus solely on efficiency, even though distribution unambiguously affects welfare, the normative maximand. The now-conventional justification for disregarding distribution is the claim of tax superiority: that the best means of influencing or correcting distribution is via tax-and-transfer. Critics have observed that optimal redistribution through tax may be politically infeasible, but have generally overlooked the rejoinder that the same political impediments to redistribution through tax will block redistribution through legal rules. This “invariance hypothesis,” as we label it, holds that there is only one distributive equilibrium and that Congress will offset through tax any deviations from it. We highlight the centrality of invariance to the conventional economic wisdom and assert that it is just as relevantly false as the zero transaction cost assumption. In contexts where political impediments to tax-based redistribution exceed the impediments to doctrinal redistribution, it may be possible to increase welfare by redistributing outside of tax. Welfarists should, therefore, devote as much scholarly attention to the “political action costs” of redistribution as they do to transaction costs.