34 C.F.R. § 303.27
(a) Parent means—
(b)
(2) If a judicial decree or order identifies a specific person or persons under paragraphs (a)(1) through (a)(4) of this section to act as the “parent” of a child or to make educational or early intervention service decisions on behalf of a child, then the person or persons must be determined to be the “parent” for purposes of part C of the Act, except that if an EIS provider or a public agency provides any services to a child or any family member of that child, that EIS provider or public agency may not act as the parent for that child.
(Authority: 20 U.S.C. 1401(23), 1439(a)(5))