he Court held that the burden of proof imposed upon the son, an
American citizen, by reason of his parent's country of origin, was an
unlawful discrimination, but it did not pass upon the constitutionality
of the Alien Land Law itself. In concurring opinions four Justices took
the position that the law was incompatible with the Fourteenth
Amendment.[1124]

Labor Relations

Objections to labor legislation on the ground that the limitation of
particular regulations to specified industries was obnoxious to the
equal protection clause, have been consistently overruled. Statutes
limiting hours of labor for employees in mines, smelters,[1125] mills,
factories,[1126] or on public works[1127] have been sustained. So also
was a statute forbidding persons engaged in mining and manufacturing to
issue orders for payment of labor unless redeemable at face value in
cash.[1128] The exemption of mines employing less than ten persons from
a law pertaining to measurement of coal to determine a miner's wages is
not unreasonable.[1129] All corporations,[1130] or public service
corporations,[1131] may be required to issue to employees who leave
their service letters stating the nature of the service and the cause of
leaving even though other employers are not.

Industries may be classified in a workmen's compensation act according
to the respective hazards of each;[1132] the exemption of farm laborers
and domestic servants does not render such an act invalid.[1133] A
statute providing that no person shall be denied opportunity for
employment because he is not a member of a union does not offend the
equal protection clause.[1134]

Women, or particular classes of women, may be singled out for special
treatment, in the exercise of the State's protective power, without
violation of the Fourteenth Amendment. Classification may be based on
differences either in their physical characteristics or in the social
conditions which surround their employment. Restrictions on conditions
of employment in particular occupations are not invalid because the law
might have been made broader.[1135] One of the earliest pieces of social
legislation to be sustained was a ten-hour law for women employed in
laundries.[1136] A law limiting hours of labor for women in hotels is
not rendered unconstitutional by reason of the exemption of certain
railroad restaurants.[1137] Night work by women in restaurants may be
prohibited.[1138] Reversing earlier decisions, th