(2) Regional partnership defined In this subsection, the term “regional partnership” means a collaborative agreement (which may be established on an interstate, State, or intrastate basis) entered into by the following: (A) Mandatory partners for all partnership grants (i) The State child welfare agency that is responsible for the administration of the State plan under this part and part E. (ii) The State agency responsible for administering the substance abuse prevention and treatment block grant provided under subpart II of part B of title XIX of the Public Health Service Act [ 42 U.S.C. 300x–21 et seq.]. (B) Mandatory partners for partnership grants proposing to serve children in out-of-home placements If the partnership proposes to serve children in out-of-home placements, the Juvenile Court or Administrative Office of the Court that is most appropriate to oversee the administration of court programs in the region to address the population of families who come to the attention of the court due to child abuse or neglect. (C) Optional partners At the option of the partnership, any of the following: (i) An Indian tribe or tribal consortium. (ii) Nonprofit child welfare service providers. (iii) For-profit child welfare service providers. (iv) Community health service providers, including substance abuse treatment providers. (v) Community mental health providers. (vi) Local law enforcement agencies. (vii) School personnel. (viii) Tribal child welfare agencies (or a consortia of the agencies). (ix) Any other providers, agencies, personnel, officials, or entities that are related to the provision of child and family services under a State plan approved under this subpart. (D) Exception for regional partnerships where the lead applicant is an Indian tribe or tribal consortia If an Indian tribe or tribal consortium enters into a regional partnership for purposes of this subsection, the Indian tribe or tribal consortium— (i) may (but is not required to) include the State child welfare agency as a partner in the collaborative agreement; (ii) may not enter into a collaborative agreement only with tribal child welfare agencies (or a consortium of the agencies); and (iii) if the condition described in paragraph (2)(B) applies, may include tribal court organizations in lieu of other judicial partners.