Randy Jackson's plan to let rabid fans flock to Michael Jackson's mausoleum is setting up a nasty battle ... with the family of another celebrity buried in the extremely private section of Forest Lawn Cemetery.
It's all over Randy's tweet, in which he said he was going to do his best to get MJ's fans "beyond the gates of Forest Lawn" to pay their respects on June 25 -- the 1-year anniversary of the singer's death.
It sounds like Randy is offering a once-in-a-lifetime opportunity, because normally non-family members can't access the mausoleum where MJ and a few other celebs are buried -- one of them being Clark Gable.
The legendary actor's grandson, Clark Gable III, told TMZ he's not down with Randy's plan ... saying the mausoleum "wouldn't be as sacred" if just anyone could go inside.
On the flip side, Randy has at least one supporter ... author Ronald J. Fields -- grandson of W.C. Fields, who's also buried there -- says he thinks fans should be allowed inside because it would be "moving to them."
Randy did not respond to our calls for comment.