Yoon Suk Yeol, South Korea’s impeached president, who is standing trial on insurrection charges over his decision to impose martial law in December, was released from a detention center on Saturday, a day after a court ruled that his detention was invalid.

The Seoul Central District Court ruled on Friday that prosecutors had violated procedural rules by holding Mr. Yoon in detention longer than legally allowed before indicting him in January. The procedural violation rendered Mr. Yoon’s detention invalid, the court said.

Prosecutors, who had a week to appeal the decision, requested instead that he be released.

Mr. Yoon smiled broadly, waving at supporters as he walked out of a detention center south of Seoul, where he had been held since Jan. 15.

His release does not affect the insurrection charge he faces in a Seoul criminal court related to his martial law declaration, or the separate proceedings at the Constitutional Court. That body is deliberating whether his parliamentary impeachment was legitimate, and if he should be formally removed from office. But it does mean that he will be free while standing trial.

This is a developing story. Check back for updates.