Were the Georgetown College Cadets once a volunteer militia?
The Georgetown College Cadets, 1889.
It seems so. According to a reference in the University Archives, the U.S. Government entered into an agreement with Georgetown College on June 13, 1838 to supply the College Cadets with Sixty short flintlock muskets. The caveat, though, was that in order to receive the muskets the Cadets had to become a volunteer militia. This agreement, titled "Regulations for the issue of arms to the Militia of the District of Columbia," is a part of Record Group 156 at the National Archives.
This first group of Cadets fizzled out and reformed in a more organized fashion in 1852. It is not clear what happened to the rifles or the Cadets' Militia status during their time of inactivity; however, it appears that the Cadets and the Government entered into other munitions agreements. Late 19th century correspondence between Georgetown President J. Havens Richards, S.J. and the War Department's Ordnance Office regarding rifles on loan to Georgetown can be found in the University Archives.