By Sam Tobin

LONDON (Reuters) – “Call of Duty” maker Activision Blizzard has been given permission to intervene in Microsoft‘s legal battle with Britain’s anti-trust regulator over its decision to block the $69 billion takeover.

Microsoft is appealing against the Competition and Markets Authority’s (CMA) decision to veto the deal, which it did in April on the grounds it could hurt competition in the nascent cloud gaming market.

The shock decision jeopardises gaming’s biggest-ever deal and drew a furious response from the companies, which questioned whether Britain remained open to tech firms.

Activision has now been given permission to intervene in Microsoft’s appeal at the Competition Appeal Tribunal, which is expected to be heard next month. That means Activision will also be able to make their case to the tribunal.

At a preliminary hearing in May, Microsoft’s lawyers accused the CMA of being a global “outlier” for blocking the Activision takeover, which has been approved by regulators including the European Union’s competition authority.

The U.S. Federal Trade Commission has also blocked the deal, a decision which is under appeal by Microsoft.

Microsoft’s president Brad Smith, who met Britain’s finance minister for talks on Tuesday, said earlier this week that the company wants to address regulators’ concerns about the Activision acquisition.