US sanctions on mixers in the past have been associated with an individual, not a piece of code. This is the first sanction to target an open source and non-custodial mixer.

A piece of code that has been actively maintained by a group of people.

Maintaining code is, in the US, likely a 1st Amendment-protected activity. Operating live services like a mixer (including any RPCs needed for Tornado) is not. (And yes I know this arrest was not made in the US, so that might be the distinction.)

> Maintaining code is, in the US, likely a 1st Amendment-protected activity.

How did the 1A defense work out for sharing "Ghost gun" CAD files?

You can take a look at the Wikipedia site for Defense Distributed, which filed suit against the state department for blocking the distribution of CAD files under export control rules. It hasn't been smooth sailing, but many of the legal cases seem to be breaking in the direction of DD. Of course that case is more complicated given that there is both a 1A and a 2A argument.

[1] https://en.wikipedia.org/wiki/Defense_Distributed

Yes. Like putting a sanction on the open Matrix protocol, and blocking any user who has interacted with it.