A federal judge on Tuesday blocked an Obama administration rule to extend mandatory overtime pay to more than 4 million workers from taking effect, imperiling one of the outgoing president's signature achievements for boosting wages. U.S. District Judge Amos Mazzant in Sherman, Texas, agreed with 21 states and a coalition of business groups, including the U.S. Chamber of Commerce, that the rule is unlawful and granted their motion for a nationwide injunction. It was to take effect Dec. 1. The rule would have doubled to $47,500 the maximum salary a worker can earn and still be eligible for mandatory overtime...