A major legal threat against Trump is dismissed. Here’s the latest.

A federal judge on Monday dismissed in its entirety the classified documents case against former President Donald J. Trump, ruling that the appointment of the special counsel, Jack Smith, had violated the Constitution.

In a stunning ruling delivered on the first day of the Republican National Convention, the judge, Aileen M. Cannon, found that Mr. Smith’s appointment as special counsel was improper because it was not based on a specific federal statute and because he had not been named to the post by the president or confirmed by the Senate.

The ruling by Judge Cannon, who was put on the bench by Mr. Trump, flew in the face of previous court decisions reaching back to the Watergate era. And in a single swoop, it removed a major legal threat against Mr. Trump just as he is set to formally become the Republican nominee for president.

Here’s what else to know in the nearly four-year case:

• Appeal expected: Mr. Smith’s team said it intended to appeal the ruling by Judge Cannon throwing out the classified documents indictment, which charges Mr. Trump with illegally holding onto a trove of highly sensitive state secrets after he left office and then obstructing the government’s repeated efforts to retrieve them.

• Possible election effects: Judge Cannon’s previous delays in this case had already all but ensured there could be no trial until after the 2024 election. If Mr. Trump wins, he could use his power over the Justice Department to have the case scuttled if it still exists.

• Undoing precedent: The ruling rolls back nearly 30 years of how special counsels have gotten their jobs. Special counsels are governed by Justice Department regulations set through the statutory authority of the attorney general. That has been the case since the Clinton administration, when the previous law on independent prosecutors was allowed to lapse in the wake of the Whitewater investigations.

• Praised by Trump: Mr. Trump celebrated the dismissal of the case in a post on his social media platform, Truth Social. He argued that all the cases against him, criminal and civil, should be dismissed “as we move forward in Uniting our Nation” after the assassination attempt against him on Saturday in Pennsylvania.

• Unusual decisions: Judge Cannon has made a host of highly unusual decisions in the classified documents case almost from the moment that she took control of it in June 2023. She has granted a serious audience to some of Mr. Trump’s most far-fetched defense claims and has repeatedly scheduled hearings for issues that many, if not most, federal judges would have dealt with on the merits of written filings. Even so, it’s fair to say that almost no one expected her to kill the documents case in quite this way at quite this moment.