President Donald Trump's campaign against U.S. Federal Reserve Chairman Jerome H. Powell is drawing criticism from both economists and legal scholars. Trump is furious with Powell for refusing to lower interest rates as much as he would like, and liberal economist Paul Krugman is warning that Trump risks a major financial crisis by trying to compromise the independence of the Fed. And many legal experts, meanwhile, are warning that it's wildly inappropriate for Trump to ask the U.S. Department of Justice (DOJ) to investigate a Fed chair simply because they have a disagreement on interest rates.But on Friday, March 13, Trump's efforts to use DOJ against Powell encountered a major roadblock thanks to Federal District Judge James E. Boasberg. In an article published on March 16, New York Times reporters Michael S. Schmidt and Alan Feuer note that federal grand juries "have repeatedly refused to charge those" being targeted by the Trump Administration and the Trump DOJ. "And now, in the wake of a lacerating ruling by a federal judge derailing an inquiry into the Federal Reserve chair, Jerome H. Powell, officials at the Justice Department have encountered an even more profound problem: Prosecutors are floundering in the most basic steps of criminal investigations into those President Trump wants scrutinized," the Times reporters explain. "The latest setback in the president's retribution campaign came on Friday when Judge James E. Boasberg of Federal District Court in Washington quashed grand jury subpoenas to the central bank for information about the renovations underway at its headquarters and Mr. Powell's testimony to Congress about them."Schmidt and Feuer add, "The U.S. attorney overseeing the case, Mr. Trump’s longtime friend and ally Jeanine Pirro, has vowed to appeal the decision and cast Judge Boasberg, who has clashed with the Trump Administration, as an activist. And an appeals court could ultimately overturn the decision. Still, Judge Boasberg's ruling was an extraordinary example of pushback by the judicial branch, cutting short the investigative process at an exceptionally early stage, when prosecutors are essentially doing the most basic work of federal law enforcement."The Times reporters stress that the "rebuke" Trump allies just got from Boasberg was especially strong."Last fall, after Mr. Trump demanded his political appointees ratchet up his retribution campaign, the Justice Department ran into roadblocks once a judge tossed out indictments against the former FBI director, James B. Comey, and the New York attorney general, Letitia James," Schmidt and Feuer report. "The prosecutor who brought the charges, the judge declared, had been appointed illegally. Then, in February, a grand jury in Washington refused to indict six Democratic lawmakers whom Mr. Trump wanted prosecuted for sedition after they released a video reminding military and intelligence personnel of their obligation not to obey illegal orders. But Judge Boasberg's block on the subpoenas against the Federal Reserve was, in some ways, an even sharper rebuke, stopping prosecutors in their tracks at the fact-gathering stage of their investigation after determining that it was flawed from the outset." The Times reporters add, "The move proved again that even though Mr. Trump has long claimed nearly boundless powers to use the law as a cudgel against his foes, he does not exercise full or unilateral control over the legal system."