How would they seize something which is decentralized (and distributed as well)?
Would they hunt all ETH miners, pools and node owners to stop DEX which use ETH smart contract?
Would they hunt the developer of the DEX, which won't stop DEX from running fine without them?
At most they would black list known coins which pass through DEX and block all website about DEX.
If I am not wrong, the domains can be easily seized. And after what happened with BTC-e/Wex.nz, I believe that in many cases the authorities will be even capable of seizing any funds within these DEX sites. But here the problem for them is that DEX sites don't usually store any coins. The coins are stored in the user wallets, even during trading.
The other possibilities that you had listed, such as closing down the ETH mining farms and blacklisting all the altcoins, are just not practical. They are difficult to implement on the ground and they may be ineffective.
Domains getting seized is very interested though, I'm interested if they'd actually do that. Does that mean DEX's will have to move to other domains or use .onion domains to prevent them from being taken down as easily?
it literally takes away the advantage decentralized exchanges had over centralized exchanges ,now what
all of the decentralized exchanges become compliant and turn into centralized exchanges?
this was expected but happened too soon , now they have only two options to comply or go rogue /hide in offshores