After graduating from Northwestern University and Harvard Law School, Barnett tried felony cases as a prosecutor in the Cook County State's Attorney's Office in Chicago.

A recipient of a Guggenheim Fellowship in Constitutional Studies and the Bradley Prize, Barnett has been a visiting professor at Penn, Northwestern and Harvard Law School.

In 2012, he was one of the lawyers representing the National Federation of Independent Business in its constitutional challenge to the Affordable Care Act in NFIB v. Sebelius.

He argues private adjudication and enforcement of law, with market forces eliminating inefficiencies and inequities, to be the only legal system that can provide adequate solutions to the problems of interest, power, and knowledge.

There have been several criticisms and reviews of his theory, including Stephan Kinsella,[2] Richard Epstein,[3] David N. Mayer,[4] Lawrence B. Solum,[5] and John K. Palchak and Stanley T.

He has advanced the Standard Model interpretation that the Second Amendment protects an individual's right to bear arms, subject to federal regulation under Congress's power to organize the militia in Article I, Section 8 of the Constitution.

[10] The question of what constitutional rights citizens possessed in the federal district has ramifications for the meaning of the Privileges or Immunities Clause of the Fourteenth Amendment.

[12][13] In February 2025, Barnett co-authored an op-ed in the New York Times with Ilan Wurman where they argue that there is no right to birthright citizenship for the children of undocumented immigrants under the Fourteenth Amendment.

[14] Ilya Somin also criticized the lack of evidence, while adding that if Barnett and Wurman's interpretation was correct, it would undermine the central purpose of the Citizenship Clause.

In short, the amendment provides a new political check on the threat to American liberties posed by a runaway federal government.

"[A] number of congressional Republicans, including soon-to-be House Majority Leader Eric Cantor" have endorsed the proposal,[17] as has Attorney General of Virginia Ken Cuccinelli.

[19] University of Texas Law Professor Sanford Levinson has said that the Repeal Amendment "ha[s] the merit of recognizing that structures matter.".

The document is an expansion of an earlier 'Federalist Amendment' that Barnett composed as part of an article he wrote in the Wall Street Journal.

Their son, Gary Barnett, attended the Georgetown University Law Center and now works as a prosecuting attorney in Brooklyn, New York.