SAN FRANCISCO — In a decisive win for Orrick, Herrington & Sutcliffe, a federal magistrate judge has refused to certify a potentially massive employee class in a suit accusing CVS Caremark Corp. of failing to pay workers and reimburse mileage for after-hours deliveries.

U.S. Magistrate Judge Elizabeth Laporte of the Northern District of California concluded plaintiffs had failed to show a uniform policy or practice at the roughly 1,000 CVS stores in California that required nonexempt employees to make off-the-clock merchandise transfers between stores without compensation.