He supported a strong federal government in economic matters, leading him to join the majority in cases such as McCulloch v. Maryland, Gibbons v. Ogden, and Fletcher v. Peck to the dismay of Jefferson and other Republicans.

Johnson's strong federalist opinions while sitting as a circuit justice for the District of South Carolina made him a social pariah in his home state.

[1]: 504  Following the siege of Charleston, both Johnson Sr. and Gadsden were imprisoned in St. Augustine, Florida by British commander Sir Henry Clinton.

[2] Johnson Jr., alongside his brother and mother (who was also a revolutionary), subsequently fled to New York City, where they lived for the remainder of the Revolution.

[8] Later that year, he was also appointed an associate justice of the state Court of General Sessions and Common Pleas, a position created by Johnson's reorganization.

[5]: 128 On March 22, 1804, President Thomas Jefferson nominated Johnson to be an associate justice of the United States Supreme Court, as the successor of Alfred Moore.

[19] Johnson also wrote over a hundred majority opinions for "arcane land, admiralty, and insurance cases" as well as numerous concurrences.

"[21] In 1808, shipowner Adam Gilchrist filed a mandamus action with the circuit court after his ship was detained following the direction of Secretary of Treasury Albert Gallatin.

Between July and October 1808, Johnson publicly debated the decision with Attorney General Caesar Augustus Rodney in a series of letters published in Charleston newspapers.

[14][8] In Fletcher v. Peck (1810), Johnson joined the majority of the Court to hold that a Georgia law voiding land grants given by the state the year prior was unconstitutional.

He did not disagree with the Court's overall holding, but he feared the case may have been "feigned" due to possible collusion between the parties in order to establish precedent.

He concurred with the majority opinion that Kentucky's legislative act to restrict the rights of titleholders to their land was illegal but once again, as in Fletcher (1810), Johnson believed that the illegality of the act was due to its violation of general principles of law, and not due to it violating the Contract Clause.

[34] In Martin, Justice Joseph Story wrote for a unanimous court that "the appellate power of the United States does extend to cases pending in the State courts, and that the 25th section of the judiciary act, which authorizes the exercise of this jurisdiction in the specified cases by a writ of error, is supported by the letter and spirit of the Constitution.

"[34]: 14  Johnson further expanded on federalism by stating that:[34]: 373 To me, the Constitution appears, in every line of it, to be a contract which, in legal language, may be denominated tripartite.

[36]: 165  Two years later, in 1821, Johnson joined the unanimous opinion written by Chief Justice Marshall in Cohens v. Virginia, which held that the Supreme Court had the ability to review state criminal proceedings.

[33] In 1822, Denmark Vesey, a free man of color, and several others were charged with allegedly planning a slave revolt in Charleston.

[37]: 119  He wrote a letter to the Charleston Courier in June 1822 and detailed an account of another previously-purported slave rebellion along the border of Georgia and South Carolina.

[9] Johnson claimed he believed the story "contained an useful moral, and might check the causes of agitation which were then operating upon the public mind" in Charleston.

Governor Thomas Bennett criticized the proceedings for being unfair since the trials were held privately, and the accused were not present when witnesses testified.

In the case of Elkison v. Deliesseline (1822), Johnson, presiding over his duties on the Circuit Court for the District of South Carolina, found that "the transfer of commerce and treaty powers to the national government eliminated state authority to enact conflicting legislation" and therefore invalidated the statute.

[41] It was the first time since 1789 that a federal court invalidated state legislation because of its conflict with the Commerce Clause[14]: 254  since it violated a treaty with the United Kingdom.

[45] In 2018, Justice Anthony Kennedy cited the concurrence in his majority opinion for South Dakota v. Wayfair Inc. and wrote that had Johnson's view "prevailed and States been denied the power of concurrent regulation, history might have seen sweeping federal regulations at an early date that foreclosed the States from experimentation with laws and policies of their own..."[46] The Georgia Gold Rush in the early 1830s led to two important cases regarding Native American sovereignty that Johnson heard on the bench.

"[50] Johnson was a pioneer of judicial restraint and believed that the legislature and executive branch had a "superior competency and fitness" to deal with evolving problems.

[31]: 129  Johnson's view on expanding federal jurisdiction, as seen in his lone dissent in Osborn v. Bank of the United States (1824), also differed from the Chief Justice's.

[31]: 129 [52] In 1807, Chief Justice Marshall, writing for the majority of the Court, granted two men who were implicated in the Burr conspiracy a writ of habeas corpus in Ex parte Bollman.

[53] According to one historian, Johnson "valued commonsense argument, factual and doctrinal accuracy, solid annotation, and full disclosure of the circumstances of the case.

One contemporary critic ridiculed it by stating that the book had a "poor developed arraignment of topics, an improper use of obscene sentences, and a dismal failure in its use of affected language.

"[5]: 130 Johnson became a social pariah in South Carolina following the nullification crisis in 1832 and 1833 because the state "was captured by a party with whose principles he unalterably opposed.

[5]: 119  It has often been reported that he was buried in the churchyard of St. Philip's Episcopal Church in Charleston, South Carolina, where a large statue of him remains.