Johnson also joined two other landmark decisions on federalism. In 1819, he joined a unanimous Court in "McCulloch v. Maryland", a case that struck down an attempt by the Maryland General Assembly to tax the Second Bank of the United States. "McCulloch" established that states could not interfere with the federal government's execution of constitutional powers and that the Necessary and Proper Clause gives Congress implied powers that are not enumerated in the U.S. Constitution. 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.