This Osler Update is a summary of the much anticipated Supreme Court of Canada decision in Seidel v. Telus Communications Inc. (Telus)which was released on March 18, 2011. At issue was whether a mandatory arbitration clause in the appellant's consumer contract with Telus meant that she could not proceed with a class action against Telus. In a ruling which appears to weaken the enforceability of arbitration clauses in both consumer and commercial agreements across the country, a narrow, five-judge majority of the Court permitted the class action to proceed with respect to one statutory claim notwithstanding the arbitration clause.