The TTABlog reports on the case here. By its terms, the statute clearly says that dilution claims, whether state or federal, are unavailable against registered marks. One would first have to bring a successful cancellation claim against the mark, then bring a dilution claim. (Under the FTDA, the ban was only on state dilution claims against federally registered marks; I worked on a case in which this ban was successfully applied by the defendant, who had a registration.)
The TTAB applied the statute as written, despite arguments that its current wording was an accident; the statute as written makes plenty of sense and the TTAB has no authority to rewrite it (nor do federal courts). One implication, apparent here, is that you can't use a dilution claim to cancel a registered mark either, or the prohibition wouldn't be any help. Another is that, if you have a famous mark, you should damn sure be monitoring what marks are published for opposition.