In this case the seller is American and shipping from Asia, so while the warranty should be 2 years in the EU, there is no way to force them as they have no presence in the EU.

The pressure is “you can’t sell this here”

They are selling it though. If I (from the EU) buy something directly from the US (or China), I don't expect EU conditions to apply. It's quite common and it's fine if both sides of the transaction understand the deal.

What's the mechanism for stopping them?

Interdiction at the ports. Seizure of persons related to the enterprise crossing into the jurisdiction.

Interdiction at the ports is the buyer's problem, not the seller's. Kidnapping people because of their employer sounds like a great way to lose tourism permanently.

Because the warranty is too short? I'll go with 'no chance' on that one.

Oh yeah, as a practical matter I totally agree though lack of enforcement invites more participation by other actors.