What is the fine-grained topic of the following text: LOS ANGELES, Feb. 15 (Xinhua) -- The western U.S. state of California, the most populous state in the country, is planning to sue the Trump administration over the president's declaration of a national emergency on the southern border with Mexico, said California Governor Gavin Newsom on Friday. Only return the topic.
California's plan to sue the Trump administration over the national emergency declaration on the southern border with Mexico.