(environmentalism advocacy group sought citizen enforcement of Clean Water Act in case in which it argued that runoff from logging roads in Tillamook State Forest required federal NPDES permit under CWA; government argued that logging operations were not industrial and that temporary nature of operations did not require permits; trial court dismissed group's claims on basis that road/ditch/culvert system was not "point source" pollutant requiring NDPES permit; Ninth Circuit Court of Appeals reversed; U.S. Supreme Court granted certiorari; government regulatory agency clarified its administrative rules after Ninth Circuit opinion, so Court required to determine jurisdiction issues; Court held statute permitted citizen suit to enforce proper interpretation of rule; Court also held issue was not moot because determining issue under prior administrative rules in favor of environmental group could require penalties to be assessed to logging operations, so groups could still have remedies; in interpreting prior administrative rule, Court deferred to agency interpretation of its administrative rules; Court upheld deference that agency’s interpretation need not be the best interpretation so long as it was not plainly erroneous; therefore, no permitting required for temporary logging operations that were not industrial; dissent filed by Scalia called for re-evaluation of Auer v. Robbins, 519 U.S. 452 (1997), which gives deference to agency interpretation of its own rules; dissent argued that allowing deference to government agencies in interpreting statutes was separate than allowing agencies to issue vague and broad rules that retain flexibility to later clarify retroactively and that agencies should be required to write clear rules and any interpretation that is different than the fairest reading is inconsistent with the regulation).