The European Union may consider expanding options available to companies to block hostile takeovers as part of a review of legislation on corporate acquisitions.

The European Commission in Brussels is examining whether firms have too little power to use defensive measures such as share-transfer restrictions or multiple voting rights to prevent a hostile takeover, according to a letter from the regulator obtained by Bloomberg News.

EU regulators have struggled to clarify how far companies can go under existing law to protect themselves against unwanted takeovers. Hermes International SCA, the maker of Birkin bags, won a waiver of French market rules to shield itself against a possible bid from LVMH Moet Hennessy Louis Vuitton SA earlier this year.