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.

Three U.S. government employee unions filed a lawsuit Monday against the Treasury, alleging that its sharing of confidential information with the Elon Musk-run Department of Government Efficiency violated the law.