MY opinion and $7.50 will get you a coffee at Starbucks.
The Second Amendment says “A well-regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.”
It is clear to me that "arms" cannot be banned by the government because of the Second Amendment. Especially so with the caveat "shall not be infringed" added to the end of the Amendment.
The question then becomes, "what are 'Arms?'" Are knives "Arms?" I would say yes. Are pistols, rifles, shotguns, and slingshots "Arms?" Undoubtedly yes, they are arms and are protected from being banned.
Are magazines "Arms?" U.S. District Judge Roger Benitez of the Southern District of California said that they are, and cannot be banned or limited in capacity, using the Heller decision of the inability to ban commonly owned arms for self defense. We shall see how much the 9th Circus mangles that well thought out decision.
So we then come to silencers, or if you prefer, suppressors. Are suppressors "Arms?" Well, one test that Judge Benitez used in his magazine ban ruling was, will the firearm function without it? In the case of a magazine, the firearm will not function as designed without a magazine, so the magazine is part of the firearm. Will a firearm operate without a suppressor? Yes, I believe it would. Therefore, is a suppressor considered "Arms" for purposes of Second Amendment protection? I think so, but it would not be a stretch to argue that they are not arms, any more than a telescopic sight or a sling can be considered "Arms." Like scopes and slings, a suppressor increases the utility of a firearm, but does not really affect the core function of the firearm in the same way that the lack of a magazine would.
So, to answer to your question, my opinion on the Constitutionality of such a ban on suppressors is that is is Unconstitutional, but by the slimmest of margins.
How does the Enumeration come into play? I think it is very significant here.
That said, this makes me think that banning suppressors is the "partial birth abortion" of the 2nd amendment debate.
Is a suppressor ban a constitutional action because it does not infringe on the use of the armament, or is it unconstitutional because we fear the slippery slope of what might follow if we accepted it?
-PJ