 Achievement of equal citizenship viewed as the removal of explicit legal barriers leaves open whether equality requires more. Even in the United States, much legal room remains for continuing controversy. The effort to establish full constitutional equal protection through the ERA foundered on assertions that differences matter to issues as diverse as military service, child support, or bathroom utilization (Mayeri 2011; Frug 1992).   This argument fueled conservative opposition to the ERA, but these issues were raised in different forms for feminists as well.  Feminists emphasizing class differences and labor rights were concerned that hard-won benefits for women could be jeopardized. Critical race theorists were concerned that formal equality for women failed to understand the complex intersectionality of discrimination against women of color (Mayeri 2011). Critics of patriarchy insisted that histories of discrimination were central to understanding the functioning of male norms in social institutions from the family to employment to political structures. At present, in US constitutional law what equal protection requires when sex is a category has not been modeled on the strict scrutiny accorded race as a category; sexual differences concretized in law must only pass a level of heightened scrutiny as to their rationale to garner constitutional acceptance.