In the case of The Mayor and Aldermen of the City of Mobile v. Miguel D. Eslava, the Supreme Court was asked to decide whether a municipal ordinance passed by the city council in 1837 was constitutional or not. At issue were two provisions: one that prohibited non-citizens from engaging in certain trades without first obtaining permission from local authorities, and another that required all foreign merchants to pay an annual fee for doing business within city limits. The court found both provisions unconstitutional because they violated due process rights guaranteed under Article IV Section 2 Clause 1 (the Privileges and Immunities Clause) of the United States Constitution which states “The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in several States” as well as other clauses protecting property rights such as Article I Section 10 Clause 1 (the Contract Clause). As a result, it ruled against Mobile's ordinance on grounds that it deprived citizens from other states their right to engage freely in commerce with no additional burden placed upon them than what is imposed upon citizens living within state boundaries.

In this case, the Supreme Court of the United States was asked to decide whether a state law that granted exclusive rights to certain individuals or companies for navigation and commerce on navigable waters within its borders violated the Constitution. The majority opinion held that such laws were constitutional because they did not interfere with Congress’s power over interstate commerce. However, Justice McLean dissented from this ruling and argued that states do not have the authority to grant exclusive privileges in matters related to interstate commerce as it is an area reserved exclusively for Congress by Article I of the Constitution. He further argued that if states are allowed to pass such laws, then it would be difficult for Congress to regulate trade between different states since each state could enact its own regulations which could conflict with those enacted by other states. Thus, he concluded that granting exclusive privileges in matters related to interstate commerce was unconstitutional and should be struck down as void.