Austin v. The Aldermen was a landmark Supreme Court case that established the principle of equal protection under the law. The case involved a dispute between the City of Boston and a black man named Alexander Austin. Austin had been denied a license to operate a livery stable in the city, despite the fact that white men had been granted similar licenses. Austin argued that the city's decision to deny him a license violated the Fourteenth Amendment, which guarantees equal protection under the law. The Supreme Court agreed with Austin, ruling that the city had violated the Fourteenth Amendment by denying him a license. The Court held that the city had discriminated against Austin on the basis of race, and that this was a violation of the Fourteenth Amendment. The Court also held that the city had failed to provide Austin with due process of law, as required by the Fourteenth Amendment. The decision in Austin v. The Aldermen established the principle of equal protection under the law, and it has been cited in numerous subsequent cases. The decision has been used to protect the rights of individuals from discrimination based on race, gender, religion, and other protected classes. The decision has also been used to protect the rights of individuals from discrimination based on sexual orientation. The decision in Austin v. The Aldermen has been cited in numerous Supreme Court cases, and it remains an important precedent in the area of civil rights.

In Austin v. The Aldermen, the Supreme Court of the United States was asked to decide whether a city ordinance that imposed an annual tax on all dogs within its limits violated the Fourteenth Amendment's Equal Protection Clause. In a 5-4 decision, Justice Field wrote for the dissenters and argued that while it is true that taxation must be equal in order to pass constitutional muster, this particular ordinance did not violate such principle because it applied equally to all dog owners regardless of race or other protected characteristics. Furthermore, he noted that since there were no restrictions placed upon how much money could be collected from each owner or any other discriminatory practices employed by local authorities when collecting taxes from citizens with pets, then there was no violation of equal protection rights under the Constitution. He concluded his opinion by stating that if Congress had intended for laws like these to be unconstitutional they would have included language explicitly prohibiting them in their legislation instead of leaving it up to courts and legislatures alike to interpret what constitutes an acceptable level of taxation without violating individual rights.