Juan Jose Gonzales, the appellant in this case, was charged with violating a law that prohibited foreign-born persons from entering the United States without first obtaining permission. The Supreme Court ruled that since Gonzales had been born in Mexico and had not obtained permission to enter the United States before doing so, he was guilty of violating the law. However, they also found that because he had resided in Texas for many years prior to its annexation by the United States and thus could be considered an inhabitant of Texas at the time it became part of America, his conviction should be reversed on appeal. In their decision they stated that although Congress has authority over immigration matters under Article I Section 8 Clause 4 of Constitution which gives them power “to establish an uniform Rule of Naturalization”; however when a territory is annexed into US jurisdiction any inhabitants who were already living there are automatically granted citizenship rights as if they were naturalized citizens. Therefore due to Gonzalez's long residence within what would become US territory upon annexation his conviction should have never occurred and must therefore be overturned on appeal.

In the case of Juan Jose Gonzales v. The United States, Justice Grier delivered a dissenting opinion in which he argued that the majority's decision was an unjustified extension of federal power over state law. He asserted that Congress had no authority to pass laws regulating slavery and therefore could not punish those who violated such laws. Furthermore, he argued that even if Congress did have this authority, it should be exercised with caution and only when absolutely necessary to protect public safety or welfare; punishing someone for merely harboring a fugitive slave did not meet these criteria. Finally, Justice Grier noted that since there were already numerous state laws governing slaves and their owners' rights, any additional regulation by the federal government would be redundant and unnecessary. In conclusion, Justice Grier believed that the majority's ruling was an unwarranted intrusion into matters traditionally left to states alone and thus should be overturned on appeal.