The Commerce Clause significantly limits the ability of States and localities to regulate or otherwise burden the flow of interstate commerce, but it does not elevate free trade above all other values. As long as a State does not needlessly obstruct interstate trade or attempt to place itself in a position of economic isolation, it retains broad regulatory authority to protect the health and safety of its citizens and the integrity of its natural resources.
Stroud, S. Shane
"The Keystone XL Pipeline and the Dormant Commerce Clause: Would Action by Congress Preclude Adequate Environmental Regulation at the State Level?,"
Utah Law Review: Vol. 2015
, Article 6.
Available at: http://dc.law.utah.edu/ulr/vol2015/iss1/6