You could always flood the network with illegal data. Core v30 didn’t enable anything new in this regard. People have been embedding wired shit on chain from the beginning. If Luke Dash jr is guilty of it.
Your scenario is absurd. Hosting a node would already be illegal because the chain already houses illegal data. It matters not if that data is in op return or embedded elsewhere.
I view this as a great test of your freedom. If a country tells me running a Bitcoin node is illegal then I know the country I’m in is not free.