Say they carry on.... How does EU actually stop people ordering from their website and getting items posted to their house?
Ordering ISPs to DNS block temu would probably be easier and effective enough.
Or maybe getting google and apple to make the app not available in the EU.
They'll put them on naughty list that will be enforced by financial institutions, i.e. it will be an infraction for credit card operators to process such a payment. Financial operators have well oiled compliance facilities and the payment won't clear. If Temu won't get the money, they won't ship the parcel. And if they won't ship, then there will be a bit less carcinogens in EU. Good stuff.
There are still borders and customs inspections, that's how.
Maybe going for the money. Forbit EU banks from transferring funds to known Temu accounts.