Whether Zucht's Fourteenth Amendment challenge to the validity of San Antonio's vaccination ordinances presented a substantial federal question that could support review by writ of error.
Holding
No. Earlier Supreme Court decisions had already made the ordinances' asserted constitutional defects insubstantial.
Reasoning
Although a municipal ordinance counts as a state law for purposes of Supreme Court review, the Court must dismiss a writ of error when the federal constitutional question is not substantial. Formal invocation of the Fourteenth Amendment is not enough to establish jurisdiction.
Jacobson v. Massachusetts had already established that a state may, under its police power, require compulsory vaccination. Thus, Zucht's claim that the school-attendance requirement effectively compelled vaccination did not present an open due-process question.
Prior cases also established that a state may delegate to municipalities the authority to decide when public-health regulations should operate and may permit local officials broad discretion in applying and enforcing health laws. The ordinances therefore did not become constitutionally suspect merely because the Board of Health had discretion over their enforcement.
The equal protection argument against the ordinances likewise lacked substance. In the exercise of the police power, government may make reasonable classifications, and a regulation need not apply to every person or setting in order to satisfy equal protection. Unlike the arbitrary licensing power condemned in Yick Wo v. Hopkins, the discretion here was of the kind needed to protect public health.