German football authorities must make sure that all clubs are treated in the same way regarding the 50+1 rule which prevents takeovers by investors, the German Federal Cartel Office said on Monday.

The cartel authority said it would close the case if the German Football League (DFL) modifies its rules accordingly.

The preliminary assessment reiterated that 50+1 does not violate antitrust laws in principle, but that the DFL must gradually end its exemption status for some clubs.

This currently applies for Bayer Leverkusen, Wolfsburg and RB Leipzig. Leverkusen and Wolfsburg are owned by chemical company Bayer and car makers Volkswagen, respectively. Leipzig are backed by drinks makers Red Bull and have only 23 voting members.

Under the 50+1 rule, which only applies in Germany, club members must have a majority of 50% of the vote, plus one.

Exceptions are possible if a a club has been backed by more than 20 years by an investor. The cartel office said that recent rulings by the European Court of Justice mean that the DFL must change its rules in this area.

“The investigations have shown that the DFL does not take sufficient care in its licensing practice to ensure that all Bundesliga and Bundesliga 2 clubs consistently offer their fans the opportunity to be admitted as full new members with voting rights,” the statement said.

“The 50+1 rule can only fulfil its objective of shaping the clubs, which can exempt it from antitrust law, if the accessibility of the clubs is strictly enforced.

“The DFL will have to ensure this in the future if it wants the 50+1 rule to be applied with legal certainty,” the cartel office said.

The cartel office said it was not investigating against the DFL but upon a request by it from several years ago for a ruling.