Wis. Stat. § 51.78: Supplementary agreements.

The compact administrator may enter into supplementary agreements with appropriate officials of other states under s. 51.75 (7) and (11). If such supplementary agreements require or contemplate the use of any institution or facility of this state or county or require or contemplate the provision of any service by this state or county, no such agreement shall take effect until approved by the head of the department or agency under whose jurisdiction said institution or facility is operated or whose department or agency will be charged with the rendering of such service.