42 CFR §433.146

1. (a)Except as specified in paragraph (b) of this section, the agency must require the individual to assign to the State—
   1. (1)His own rights to any medical care support available under an order of a court or an administrative agency, and any third party payments for medical care; and
   2. (2)The rights of any other individual eligible under the plan, for whom he can legally make an assignment.
2. (b)Assignment of rights to benefits may not include assignment of rights to Medicare benefits.
3. (c)If assignment of rights to benefits is automatic because of State law, the agency may substitute such an assignment for an individual executed assignment, as long as the agency informs the individual of the terms and consequences of the State law.