If it fired fixed ammunition, it would be a short barrel shotgun under the federal law.
In fact, the LeMat "back in the day" was rare (I doubt anyone ever carried six, and very few carried even one) and not considered very reliable, something the C.S. inspectors reported time and again. The Confederacy contracted for 2000, for use by the C.S. Navy, but I believe only about 100 were delivered. Other shipments were in dribs and drabs, 100 here, 3 there.
Late shipments were apparently never received; as the Union blockade tightened they were either left in Jamaica or remained in England. Some were sold in London after the war.
Le Mat himself was an American, but the guns were made in France; an early attempt to have them made in New Orleans failed. He was the inventor but was not a gun maker or even a real businessman. He may have had some connection to Gen. P.G.T. Beauregard, since some revolvers were sent to the general for distribution to high ranking officials and officers, a practice common in those days.
A figure is sometimes given as over 2500 revolvers made, based on known serial numbers, but it is fairly certain that less than 500 actually reached the Confederacy, and some writers say less than that. The reason was that deliveries from Europe were about as unreliable as the U.S. Navy could make them, and shipments might or might not get through.
As with other Confederate weapons, far more have been made in Italy in the last 50 years than were ever used by the C.S. armed forces.
Jim