Mont. Code Ann. § 81-23-106

This chapter does not apply to foreign or interstate commerce except insofar as it may be effective in compliance with the United States constitution and with the laws of the United States. It is the intention of the legislature, however, that the instant, whenever that may be, that the handling within the state by a dealer of milk produced outside of the state becomes the subject of regulation by the state in the exercise of its police powers, the provisions of this chapter affecting intrastate milk immediately apply and the powers conferred by this chapter attach thereto.