The Mayor and Aldermen of the City of Mobile brought a case against J. Emanuel and G.S Gaines in 1843, arguing that they had violated an ordinance prohibiting African Americans from selling goods within city limits without permission from the mayor or board of aldermen. The defendants argued that this ordinance was unconstitutional as it violated their right to equal protection under the law, as well as their right to pursue any lawful trade or business without discrimination on account of race or color. The Supreme Court ultimately sided with Emanuel and Gaines, ruling that such ordinances were indeed unconstitutional due to their violation of both state and federal laws protecting citizens’ rights regardless of race or color. This decision set an important precedent for future civil rights cases by establishing legal protections for individuals based solely on racial identity rather than economic status alone.

In the case of Mayor and Aldermen of the City of Mobile v. J. Emanuel and G. S. Gaines, the dissenting opinion argued that a state law granting exclusive rights to operate ferries across certain rivers was unconstitutional under Article I, Section 10 of the United States Constitution which prohibits states from passing any law impairing contracts without due process or just compensation for those affected by it. The majority opinion held that this particular state law did not violate Article I, Section 10 because it only regulated commerce on navigable waters within its borders rather than interfering with existing contracts between individuals or corporations; however, Justice Catron disagreed with this interpretation and argued that since there were already ferry operators in existence at the time when this new legislation was passed who had invested money into their business operations based upon an expectation that they would be able to continue operating them as before without interference from government regulations then these businesses should have been compensated for any losses incurred due to such regulation if it is found to be constitutional otherwise it would amount to an unconstitutional taking away of private property without due process or just compensation as prohibited by Article I, Section 10 .