According to a report on Wines And Vines the EU have changed the labelling regulations to prohibit the use of certain terms by non-EU members. Those terms apparently include "chateau", "vintage" and "clos".
Now I'm 100% behind protecting specific regional terms that get abused in America, such as Champagne or Burgundy (and Cheddar for that matter), but we are talking about some generally accepted terms. The word Château is abused by the French as much as anyone; the majestic château on the label of Léoville-Barton is in fact the Château Langoa Barton. And Clos simply means a walled or enclosed vineyard.
In the end it's probably just another bargaining chip for the EU in trade negotiations; doubtless an agreement will eventually be thrashed out. With luck it'll end the "grandfathering" abuse of the terms above and we can all forget about it.