China's ban on the U.S. chipmaker Micron signals Beijing's willingness to use more aggressive legal tools against Western technology companies in response to the United States and its allies' expanding export restrictions, which will only further compel foreign firms in the sector to reduce their exposure and sales to China. Following an investigation that appears to have lasted less than two months, the Cyberspace Administration of China (CAC) announced on May 21 that it would ban China's critical infrastructure operators from using chips produced by U.S. semiconductor manufacturer Micron. According to the CAC, Micron's products had ''serious network security risks'' that ''pose significant security risks to China's critical information infrastructure supply chain, affecting China's national security.'' The restrictions are narrower than the blanket ban some had feared, and Micron's memory chips are primarily used in consumer electronics devices (such as smartphones and laptops). But Chinese technology companies seeking to maintain...