Is a delegation of Congressional power an 'agency order' or 'agency action' such that a party wishing to challenge that delegation must file that challenge with the agency under the administrative-review-scheme-of-15-usc-717r, or is the proper-forum-for-constitutional-challenges the-district-court?

QUESTIONS PRESENTED I. Is a delegation of Congressional power an “agency order” or “agency action” such that a party wishing to challenge that delegation must file that challenge with the agency under the administrative review scheme of 15 U.S.C. § 717r, or is the proper forum for constitutional challenges the district court? II. Is an administrative agency’s test for determining “public use” for purposes of eminent domain an “agency order” such that a party wishing to challenge that test as unconstitutional must file that challenge with the agency and adhere to its administrative review scheme, or is the proper forum for constitutional challenges the district court?