"The thirteenth amendment is both libertarian and egalitarian, because the paradigmatic violation, antebellum slavery, deprives its victims of both liberty and equality. It compelled some private individuals to serve others, and it did so as part of a larger societal pattern of imposing such servitude on a particular caste of persons. If the libertarian and egalitarian rules of decision are both plausible readings of the amendment, it is because each stresses one undeniable aspect of the paradigmatic case. Th Court may invalidate laws that impose servitude only on individuals, as it said it was doing in Bailey, and Congress may outlaw practices that stigmatize, but do no more than stigmatize, traditionally subjugated groups, as in Jones. But if either of these cases were paradigmatic of the amendment reaches far enough to forbid either of these injuries standing alone, a fortiori it forbids practices that inflict both of them at once. Compulsory pregnancy is such a practice."