Are they??

Virginia DF&G Regulation: G. A muzzleloading gun, for the purpose of this section, means a single shot flintlock or percussion weapon, excluding muzzleloading pistols, .45 caliber or larger, firing a single projectile or sabot (with a .38 caliber or larger projectile) of the same caliber loaded from
the muzzle of the weapon and propelled by at least 50 grains of black powder (or black powder equivalent or smokeless powder).

From Tahquamenon:Nitrocellulose or Smokeless Powder
Smokeless powder is actually nitrocellulose-based powder, the material developed by Paul Vieille in 1884. Nitrocellulose required much more processing than simply dipping cotton in acid and wood pulp soon became the preferred source of raw cellulose. The two sources of raw cellulose have different properties so they are used and blended based upon the intended purpose of the finished product. To make nitrocellulose powder, the nitrocellulose is dissolved in a mixture of ether and alcohol and it becomes a gelatinous mass. When the solvents evaporate, it leaves a hard plastic material. The gelatinous blob is usually rolled into a sheet before it hardens and after it hardens it is cut up into various sized flakes. The cutting is done on machines because the particles are tiny and it takes a great deal of cutting. Furthermore, it just wouldn’t have been the Industrial Revolution if they had cut it by hand. Nitrocellulose was the first reliable and stable gunpowder. It is the principle type of propellant today.

If I lived in VA, I would request a further clarification and definition of this regulation.
Question(s): What is defined as smokeless powder? Are they including nitrocellulose (smokeless) powder? And, if they are truly meaning a 50 grain Minimum, that could be excessive for ML's rated for nitro-powder depending on the Nitro-powder type. Particularily if one measures by volume which the measuring device and method could add 5gr or more variance from charge to charge. You should never use a BP measuring device for smokeless powder, you should use a scale to measure the charge and if you use Lee Dipper measuring devices, you should still verify the load on a scale.

The 50Grain Minimum load in the regulation is over the recommended loads for the Savage 10MLII using smokeless, so I have a hunch that the Virgina DF&G is not intending Nitrocellulose smokeless powder as a BP equivelant. Savage specifies a 2-Grain maximum variance with Nitro-Powder. So the VA DF&G reg would mandate that you overload your 10MLII in every instance if using Nitrocellulose power.

http://www.savagearms.com/images/pdf/manuals/MLII_loads.pdf

Now for BP or BP Substitues (777, Pyrodex, BM3, etc,) a 50gr minimum load by volume would ensure a reasonable baseline for game harvesting lethality. I don't know anyone that deer hunt's with a .45 and less than 50 gr charge and a PRB nor anyone that would hunt with less than 50gr in anything .45 or larger.

I would say the Virgina as some further definition and clarification required - to say the least.

Tahquamenon