How is it different? They are tools that can be used for both legal and illegal means. If you put legal responsibility on one toolmaker to ensure their tools are not used in an illegal fashion, why wouldn't you do the same for other toolmakers?
An exploit is to encryption as a sword is to a shield.
We don't regulate shields.
Stop trying to find gotchas. Weapons (read: items whose primary goals are to inflict damage, maim, kill, injure, destroy) are and should be regulated.
That's your mistake right there
I wonder what the rationale behind this federal law is. Does wearing/purchasing armor indicate that you, convicted felon, are simply up to no good once again? Is it one of those "you don't need ~~privacy~~ armor if you don't have anything to hide" things?
[1] https://www.shotstop.net/resources-1/2020/9/8/is-it-legal-to...