Because the degree of sound suppression the device produces is legally irrelevant.
Because of the specific wording of the law, it is the intent to silence a firearm (without prior Fed approval) that is the crime.
SO, it is technically possible you could be convicted of violating the law even if the silencer doesn't work (reduce noise a measureable amount).
it is also technically possible that someone building a muzzle brake type device, that unintentionally reduced the sound level could be found innocent of violating the law. (although how one could convince a court of this, I have no idea).
With all due respect, I don't think that is exactly correct. It is more like intent + effect.
As ATF pointed out in its briefs for this case, a pillow may be effective as a silencer. Yet, because that was not the intent with which the pillow was made, it is not considered a silencer under the law. A potato can be used as a silencer (single use), but that is not its intended use. However, if you use a potato or pillow as a silencer, you could still be charged with illegal possession of a silencer (if it is not registered).
On the other hand, making a part for a silencer, like a baffle, end cap, or tube, with the intent that it be used in a silencer is still covered even though it alone will not have any sound reducing effect. However, if you make a muzzle brake with no intent that it muffle the report, it will still be a silencer under the law if it has that effect. Lack of intent does not negate effect, unless the item has some common and unrelated use. The "solvent catch adapters" that allow you to screw a can or oil filter onto a barrel really push the line. The "other" use and intent is not strong on credibility. And once the can or filter body has an exit hole, it doesn't matter what you claim was your intent, the effect is there and you possess a silencer.
The statute says:
The terms "firearm muffler" and "firearm silencer" mean any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication.
The "and intended for use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication" relates to "including any combination of parts, designed or redesigned," not to the first clause. The law will find that "any device for silencing, muffling, or diminishing the report of a portable firearm" is a silencer, unless it has some other obvious purpose or intent
and is not used for the purpose of "silencing, muffling, or diminishing the report of a portable firearm."
The Judge explained:
Even if the purpose of a device is relevant to determining whether it is "for diminishing the report" of a gunshot—and it very well may be—that does not lead to the conclusion that the government seeks: that the device's actual effectiveness as a silencer is totally irrelevant. To use an example, a regulation might define a "space heater" as a device "for increasing the amount of heat" in a room. In determining whether a certain device was a "space heater," one fact that a rational agency would surely consider was whether the device actually gave off any heat. On the contrary, if the agency knew that a certain device was incapable of emitting heat, that should certainly affect the agency's conclusion as to whether that device was a space heater. ATF may be right that a device's purpose is relevant to classifying it—especially when the statute uses the word "for"—but that does not mean that the device's effectiveness or capabilities are irrelevant.
So while intent is
relevant to the determination, so is effect.
