Zecharian Chafee was born in Providence to a political family descended from Roger Williams. Chafee attended Brown, where he was a fellow. After graduating fron Brown in 1907, he went on to study law at Harvard University. While attending Harvard, he became influenced by the theories of sociological Jurisprudence presented by Roscoe Pound and others at Harvard. He taught law at Harvard until 1956. He recieved an LL.D. from Brown jun 1916 and an honorary degree in 1937.
Chafee was known as an authority on equity, interpleader, negotiable instruments, and unfair business competition. Chafee drafted the Federal Interpleader Act of 1936 (49 Stat. 1096), considering this his foremost professional accomplishment. He also became an expert on congressional apportionment and helped apportion seats in the United States House of Representatives based on the 1930, 1940 and 1950 censuses. He was one of tweleve lawyers who reported on illegal activities of the Department of Justice in 1920. In 1921, he was brought before the Harvard Board of Overseers on a charge of radicalism, but defended himself strongly enough to keep his job. From 1929 to 1931 Chafee was a consultant to the National Commission on Law Observance and Enforcement ( the Wickersham Commission) for which he co-author of report on lawlessness in law enforcement in 1931.
Chafee wrote a number of significant works on civil liberties. Freedom of Speech, his first, established modern First Amendment theory. Chafee was inspired by the United States’ suppression of radical speech and ideas during the First World War to edit and update a collection of several of his journal articles addressing significant World War I cases, including those of Emma Goldman. In 1941, Chafee revised and reissued Freedom of Speech as Free Speech in the United States, which became a leading treatise on First Amendment law. His writing was a major influence on Oliver Wendell Holmes and Louis Brandeis, whose jurisprudence established the First Amendment as a significant source of civil liberties. Chafee continuted to chamption civil liberties throughout the 1930s and 1940s as a member of the American Bar Association’s Bill of Rights Committee. From 1943 from 1947 he served as vice-chairman of the Commission on the Freedom of the Press. Senator Joseph McCarthy described Chafee as "dangerous" to the United States.
In the 1940s and 1950s, Chafee became an advocate for international human rights and served as a representative on the United Nations Subcommission on Freedom of Information and the Press. He was a United States delegate to the 1948 United Nations Conference on Freedom of Information and the Press.
From 1956-1957, Chafee was a Lowell Television Lecturer on WGBH. He completed a 16 lecture television series "The Constitution and Human Rights", an adaptation of a general education course he developed in 1950.