Any provision of any contract, which provision prohibits any transfer of any contractual interests thereunder, or any commingling or transportation of natural gas subject to such contract with natural gas the sale for resale or transportation of which is subject to the jurisdiction of the Commission under the Natural Gas Act [
15 U.S.C.
717 et seq.], or terminates such contract on the basis of any such transfer, commingling, or transportation, shall be unenforceable in any court of the United States and in any court of any State if applied with respect to any transfer approved under the rule required under subsection (a)(1) of this section.