Washington regulators tightened their focuson the tech industry’s biggest players Tuesday — but a judge showed how big a fight the feds may have on their hands.

The two actions came just hours apart: The Federal Trade Commission said it was launching an open-ended study into a decade’s worth of mergers and acquisitions by Amazon, Apple, Facebook, Google and Microsoft, an inquiry that could be a prelude to trying to undo some of those past deals. But separately, a federal judge in Manhattan refused to block the $26.2 billion merger of Sprint and T-Mobile, in yet another sign that the courts have set a high bar to proving that corporate marriages lessen competition and harm consumers.

U.S. District Judge Victor Marrero’s ruling showed the headwinds that federal and state enforcers will face if they mount a serious effort to block future Silicon Valley acquisitions — let alone bust up years-old deals, as politicians like Elizabeth Warren have advocated.

“After something like this, good luck going after the tech companies,” said Gigi Sohn, a fellow at the Georgetown Law Institute for Technology Law & Policy, who served in the Federal Communications Commission during the Obama administration. “Particularly if you want to break up the companies in some way, I don’t know how you do it.”

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