Ropes & Gray on Monday became the first big law firm to weigh in on a case before the U.S. Supreme Court challenging a California court ruling that invalidated a former Winston & Strawn partner’s employee-arbitration agreement.

Douglas Hallward-Driemeier, head of Ropes & Gray’s appellate and Supreme Court practice, wrote in an amicus brief—filed in support of Winston & Strawn—that his firm’s lawyers “handle highly confidential attorney-client privileged information and highly confidential business information every day. The California Court of Appeal’s decision impedes the firm’s ability to rely on confidential arbitrations to protect this sensitive information from public disclosure.”