The Commission may not, during the 10-year period beginning on November 9, 1978, revoke or amend any certificate of public convenience and necessity issued before January 1, 1969, under section 7 of the Natural Gas Act [15 U.S.C. 717f] for the transportation of natural gas owned by any electric utility except upon the application of the person to whom such certificate was issued.

The limitation under subsection (a) shall not affect the authority of the Commission to enforce any curtailment of deliveries of natural gas under the Natural Gas Act [15 U.S.C. 717 et seq.].