Michael Wolff tried pulling a legal fast one on Melania Trump ... at least according to the federal judge who just tossed his case.

Wolff -- the longtime Trump biographer behind books like "Fire and Fury" -- sued after Melania's lawyers threatened him with a $1 Billion defamation lawsuit tied to comments he made linking her to late pedophile Jeffrey Epstein.

But on Friday, a federal judge completely shut down Wolff’s lawsuit ... accusing him of "gamesmanship," "forum-shopping,” and abusing the judgment process by trying to beat Melania to the courthouse before she could sue him herself.

The judge said Wolff was essentially trying to "short-circuit" the normal legal process by asking the court to rule ahead of time that he didn’t defame FLOTUS ... instead of waiting for the actual defamation case to play out the normal way.

At one point, the ruling mocked Wolff's side for relying on things like the "Melania" documentary, public appearances by the Trumps, and speculation about the Melania and President Trump's marriage dynamic.

Even so, the judge ultimately refused to let Wolff's lawsuit move forward ... dismissing the entire thing and saying if Melania wants to sue him for defamation, she can do it the traditional way in court.

The judge even said the court would not be "conscripted to oversee an abusively presented spat" between the two sides.