Debbie Rowe, mother of Prince Michael, 6, and Paris, 5, was concerned that the group led by Louis Farrakhan would influence her children, whom she recently revealed were Jewish by birth, the Evening Standard reported Monday.
A source in Rowe's camp told the New York Post: "If there wasn't something in writing, something in the media, then he would have been served" with legal papers.
The Nation of Islam handled Jackson's security last month when he appeared in a California court to deny seven counts of molesting a teen and two counts of administering an intoxicating agent.
Jackson has denied the Chicago-based group is involved in his business affairs and a spokesman said they would take a lesser role in his security.
A California judge set April 2 as the court date for a preliminary hearing on the molestation charges.