Semasa era kolonial Amerika, semua lelaki muda yang sihat tubuh badan adalah anggota militia, bergantung pada undang-undang negeri masing-masing.[2] Setiap bandar membentuk militia tempatan yang bebas untuk mempertahankan diri sendiri.[3] Setahun sebelum Perlembagaan Amerika Syarikatdiratifikasi, The Federalist Papers memperincikan pengasas' utama militia pada tahun 1787.[4][5] Perlembagaan baru memberi kuasa kepada Kongres untuk "menyusun, melengkap, dan mendisiplinkan" pasukan tentera kebangsaan ini, memberikan kawalan utama kepada setiap kerajaan negeri.[6][7]
Hari ini, seperti yang ditakrifkan oleh Akta Militia 1903, istilah "militia" digunakan untuk menerangkan dua kelas dalam Amerika Syarikat:[8]
Militia tersusun – terdiri daripada pasukan militia Negeri; terutamanya, Pengawal Kebangsaan dan Militia laut.[9] (Nota: Pengawal Kebangsaan tidak boleh dikelirukan dengan Pengawal Kebangsaan Amerika Syarikat.)
Militia tidak tersusun – merangkumi Militia Simpanan: setiap lelaki sihat tubuh badan yang berumur 17 tahun dan dibawah 45 tahun, bukan anggota Pengawal Kebangsaan atau Militia Laut.[10]
^Spitzer, Robert J.: The Politics of Gun Control, Page 36. Chatham House Publishers, Inc., 1995.
^Justice Scalia, Opinion of the court. SUPREME COURT OF THE UNITED STATES DISTRICT OF COLUMBIA, et al., PETITIONERS v. DICK ANTHONY HELLER: on writ of certiorari to the united states court of appeals for the district of columbia circuit. 2008. "... the 'militia' in colonial America consisted of a subset of 'the people'—those who were male, able bodied, and within a certain age range."
^Young, David E. The American Revolutionary Era Origin of the Second Amendment's Clauses. JOURNAL ON FIREARMS & PUBLIC POLICY, Volume 23. 2011. Extended excerpt from Mason's Fairfax County Militia Plan. 1776.
^The Federalist Papers No. 29, Hamilton, Alexander. Concerning the Militia. Daily Advertiser. 1788.
"What plan for the regulation of the militia may be pursued by the national government, is impossible to be foreseen ... were the Constitution ratified ... 'The project of disciplining all the militia of the United States is as futile as it would be injurious, if it were capable of being carried into execution.'"
^The Federalist Papers, No. 46, Madison, James Jr. New York Packet. 1788.
"... the State governments, with the people on their side, would be able to repel the danger. ... a militia amounting to near half a million citizens [~1/5 of the free population] with arms in their hands, officered by men chosen from among themselves, fighting for their common liberties, and united and conducted by governments possessing their affections and confidence."
^U.S. Constitution, Article I, Sec. 8 : "Congress shall have the Power ... To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions;
To provide for organizing, arming, and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United States, reserving to the States respectively, the Appointment of the Officers, and the Authority of training the Militia according to the discipline prescribed by Congress;"
^U.S. Constitution, Article II, Sec. 2, Clause 1: "The President shall be the Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States when called into the actual service of the United States."
^Department of Defense, Under Secretary of Defense for Personnel and Readiness, Military compensation background papers, Seventh edition, page 229. Department of Defense, 2005.
^Beard, Charles Austin: Readings in American Government and Politics, Page 308. Macmillan, 1909. "Sec. 1. That the militia ... shall be divided into two classes ... the organized militia, to be known as the National Guard ... and the remainder to be known as the Reserve Militia."