The Treasury Department was accused of breaking federal law by giving Elon Musk’s team of government efficiency enforcers access to a trove of personal and financial information — setting up a legal showdown over the Trump administration’s signature effort to shrink the government.

A senior U.S. lawmaker says representatives of Elon Musk were granted “full access” to a U.S. Treasury payments system used to disperse trillions of dollars to Americans each year, and warned that Musk’s access to the system poses a “national security risk.”