One example arose in Muller v. Oregon (1908), in which the Court upheld a maximum hours law that applied to women... on a theory that probably seems a tad offensive now:
That woman's physical structure and the performance of maternal functions place her at a disadvantage in the struggle for subsistence is obvious. This is especially true when the burdens of motherhood are upon her. Even when they are not, by abundant testimony of the medical fraternity continuance for a long time on her feet at work, repeating this from day to day, tends to injurious effects upon the body, and, as healthy mothers are essential to vigorous offspring, the physical well-being of woman becomes an object of public interest and care in order to preserve the strength and vigor of the race.
Still again, history discloses the fact that woman has always been dependent upon man. He established his control at the outset by superior physical strength, and this control in various forms, with diminishing intensity, has continued to the present. As minors, thought not to the same extent, she has been looked upon in the courts as needing especial care that her rights may be preserved . . . . [I]t is still true that in the struggle for subsistence she is not an equal competitor with her brother . . . . Differentiated by these matters from the other sex, she is properly placed in a class by herself, and legislation designed for her protection may be sustained, even when like legislation is not necessary for men, and could not be sustained.Fast-forward 15 years, and the Supreme Court welcomed women to the liberty of contract club in Adkins v. Children's Hospital (striking down a minimum wage law that applied only to women):
[T]he ancient inequality of the sexes, otherwise than physical, as suggested in the Muller Case has continued ‘with diminishing intensity.’ In view of the great—not to say revolutionary—changes which have taken place since that utterance, in the contractual, political, and civil status of women, culminating in the Nineteenth Amendment, it is not unreasonable to say that these differences have now come almost, if not quite, to the vanishing point. In this aspect of the matter, while the physical differences must be recognized in appropriate cases, and legislation fixing hours or conditions of work may properly take them into account, we cannot accept the doctrine that women of mature age, sui juris, require or may be subjected to restrictions upon their liberty of contract which could not lawfully be imposed in the case of men under similar circumstances. To do so would be to ignore all the implications to be drawn from the present day trend of legislation, as well as that of common thought and usage, by which woman is accorded emancipation from the old doctrine that she must be given special protection or be subjected to special restraint in her contractual and civil relationships.History has not been kind to the liberty of contract cases - but the Adkins Court should at least get some credit for its enlightened view of women, right?