Mont. Code § 2-1-208
The consent of the state of Montana to the purchase by the United States of lands within the state of Montana to be embraced in Yellowstone national park, other than the lands described in 2-1-207, and the consent of the state of Montana to the exercise of legislative jurisdiction by the United States over any additional lands to be embraced in said national park, as such consents may be contained in the act of the second legislative assembly of the state of Montana approved February 14, 1891, entitled, "An Act Ceding to the United States Jurisdiction Over Certain Lands" or any amendment of said act is hereby withdrawn, and exclusive legislative jurisdiction over all lands within the state of Montana that may be added hereafter to said national park shall be retained in the state of Montana.
§ 2-1-208, MCA