For the first time ever, a European appeals court on Thursday annulled a European Commission deal approval, saying regulators should never have cleared the music merger between Sony Corp. and Bertelsmann AG.

Legal experts say that while the ruling may mean the ultimate unravelling of the 2004 deal creating Sony BMG Music Entertainment, the world’s No. 2 music company, they see its impact as far wider on all deals — music and otherwise — in sectors dominated by a handful of powerful players.