R.I. Gen. Laws § 15-7.1-3: Supplementary agreements.

The compact administrator is authorized and empowered to enter into supplementary agreements with appropriate officials of other states pursuant to the compact. In the event that the supplementary agreement requires or contemplates the provision of any service by this state, the supplementary agreement shall have no force or effect until approved by the head of the department or agency which will be charged with the rendering of the service.