John Forrest Dillon (December 25, 1831 – May 6, 1914) was an American jurist who served on both federal and Iowa state courts, and was the author of a highly influential treatise on the power of states over municipal governments.

Dillon studied medicine at Iowa State University at the age of 19. Shortly after beginning his practice he abandoned it to study law, and was admitted to the Iowa bar in 1852. He was elected as the Scott County prosecutor after a brief private practice in 1853, and was then elected to a judgeship in Iowa's 7th Judicial Circuit in 1858. He was elevated to the Iowa Supreme Court in 1862 and served until 1869, when he was appointed by President Grant to the Eighth Circuit.

While on the federal bench, Dillon wrote Municipal Corporations (1872), which was one of the earliest treatises to systematically study the subject. Dillon explained that in contrast to the powers of states, which are presumed unlimited in the absence of express restrictions under the state or federal constitution, municipalities only have the powers that expressly granted to them. His formulation of the scope of municipal power came to be known as the "Dillon Rule": municipal governments only have the powers that are expressly granted to them by the state legislature, those that are necessarily implied from that grant of power, and those that are essential and indispensible to the municipality's existence and functioning. If there is an ambiguity in the grant of power, this should be resolved against the municipality, so that its powers are narrowly construed. However, when the state has not specifically directed the method by which the municipality may implement its granted power, the municipality has the discretion to choose the method so long as its choice is reasonable.

Hundreds of U.S. court decisions to the present day have employed the Dillon Rule to determine the scope of municipal powers and rights. Critics of the Rule have argued that it imposes unreasonable constraints on the ability of communities to govern themselves and so undermines democracy, and even that local self-government is a matter of natural right that does not need to be conferred by higher political structures. It has also been suggested that Dillon's approach derived from the contemporary view that cities were inherently corrupt political organs. This was perhaps an often well-deserved judgment during his time, especially considering the extensive business ties and even investments of numerous cities and their leaders in the late 19th century. Deviations from the Dillon Rule remain in the minority, however, despite the significant decrease in the public perception of municipal corruption.

The Supreme Court of the United States cited to Municipal Corporations and fully adopted Dillon's emphasis on state power over municipalities in Hunter v. Pittsburgh , 207 U.S. 161 (1907), which upheld the power of Pennsylvania to consolidate two cities against the wishes of the majority of the residents in one. The Court's ruling that states could alter or abolish at will the charters of municipal corporations without infringing upon contract rights heavily relied upon Dillon's separation of public, municipal corporations from private ones.

Dillon was also the author of Removal of Cases from State Courts to Federal Courts and Municipal Bonds, both in 1876. After leaving the Circuit Court, Dillon was a professor at Columbia Law School from 1879 until 1882, where he taught real estate and equity. He then taught at Yale Law School from 1891 until 1892, during which time he also served as the president of the American Bar Association. Dillon then returned to private practice until his death in 1914 in New York City.

A memorial fountain to Dillon was erected in downtown Davenport, Iowa in 1918.

Dillon's oldest son, Hiram Price Dillon (1855 – 1918), also became a lawyer in Iowa, and a Master of Chancery in federal court.

References

• Gerald E. Frug, et al. Local Government Law, 3rd ed. pp. 139-158. West Publishing, 2001.
• See Arlington County v. White, 528 S.E.2d 706 (Va. 2000), for a modern use of the Dillon Rule to invalidate municipal action. See State v. Hutchison, 624 P.2d 1116 (Utah 1980) for an example of the minority, critical view.