US retail giant Wal-Mart has filed a lawsuit against the Puerto Rican justice department to prevent it from blocking the retailer's acquisition of a local supermarket chain. The lawsuit accuses the justice department of discrimination in pursuing an antitrust action to block Wal-Mart's purchase of Amigo supermarkets. A Wal-Mart spokesman told a local radio station that the company suspects a different measurement of being used from what has been used in the past. The Wal-Mart lawsuit names as defendant Justice Secretary Anabel Rodriguez, who had confirmed the government's intention to sue Wal-Mart to apply local antitrust laws, reported AP.