Kardashians -- Fireworks Investigation Goes Boom!! D.A. Rejects Case

Bust out the M80s -- Kris Jenner and Khloe Kardashian can celebrate dodging criminal charges for that massive fireworks display they set off in the middle of the night ... terrifying beach residents.

Law enforcement sources tell us the L.A. County Sheriff's Department wrapped its investigation into the explosive yacht party Khloe threw for James Harden's birthday early in the morning of August 26th.

We're told the Sheriff's Dept. presented its findings to the LA. County District Attorney, and recommended a misdemeanor charge of disturbing the peace -- but the D.A. rejected it because the Kardashians had "passive permission."

We broke the story ... the Coast Guard gave the Sheriff a heads up that Kris' production co. would be lighting up the sky that night, and didn't need a permit since the boat was outside the marina. Still, angry residents wanted the Sheriff to bust them for violating noise ordinances.

Had they prosecuted, it's unclear who would take the fall -- Kris, Khloe, or the fireworks vendor -- but it's a moot point now ... criminally, anyway.

We're told a group of residents is still pushing forward with a small claims lawsuit.