For many defense lawyers, winning a ruling that could stem the tide of shareholder lawsuits would be a career-defining achievement. For Bradley Ruskin of Proskauer Rose, it was the icing on the cake in an influential sports law case he’s dominated from start to finish.

The Delaware Supreme Court ruled on May 8 that the professional tennis organization ATP Tour Inc. lawfully adopted bylaws requiring members to pay ATP’s legal bills if they sue the organization and lose. The ruling came in an unusual antitrust case over ATP’s reorganization of its tournament calendar, but experts say it will deter plaintiffs lawyers behind a barrage of shareholder suits targeting corporate mergers and acquisitions.