Going by the history of list price differences, it doesn't look like the EU could shut anybody down either (strangely enough). Otherwise they wouldn't have bothered publishing lists for the last fifteen years, they just would have forced the automakers to comply in year 1 and the issue would have been over.
It appears that the reason the lists were published was to make the pricing differences in various countries more visible to the public, who could then more easily punish (if they so chose) the offending automakers by purchasing those who were pricing more fairly (or whatever else).
Nothing like having a recently updated, official list of the pricing differences of various makes and models before going car shopping. Something to smack down on the salesman's desk, give some teeth to the angry letter to the newspaper, etc. Seems like eventually it worked.