In the case of Sun Oil Co. v. Federal Power Commission, 1959, the Supreme Court dealt with issues related to natural gas regulation and pricing. The dispute arose when Sun Oil Company challenged an order by the Federal Power Commission (FPC) that required it to refund a portion of increased rates charged for its interstate sale of natural gas. The FPC had suspended these rate increases temporarily under Section 4(e) of Natural Gas Act but allowed them provisionally subject to later determination on their reasonableness and potential refunds if found excessive. Sun argued that this was beyond FPC's authority as they could only determine future rates not past ones; however, the court disagreed stating that Congress intended such provisional collections be subject to refund in order to protect consumers from unreasonable charges while allowing companies some flexibility in adjusting their prices. The Supreme Court upheld FPC’s decision asserting its power over regulating both prospective and retrospective aspects within reasonable limits under Natural Gas Act provisions thus affirming consumer protection against unjust or unreasonable costs.

In the dissenting opinion for Sun Oil Co. v. Federal Power Commission, Justice Brennan argued that the majority's decision to uphold a ruling by the Federal Power Commission (FPC) was incorrect because it failed to properly interpret and apply relevant provisions of the Natural Gas Act. He contended that under this act, independent producers like Sun Oil were not subject to FPC jurisdiction unless they were engaged in interstate commerce or their activities directly affected such commerce. In his view, there was no evidence showing that Sun Oil’s operations met these criteria; thus, he believed its rates should not be regulated by FPC as if it were a natural gas company involved in interstate transactions. Furthermore, Justice Brennan criticized the majority for giving too much deference to administrative agencies' interpretations of statutes at expense of judicial review and statutory interpretation principles.