This educational guide is based on the linked primary sources. It is not a Court publication, is not affiliated with the Court, and is not legal advice.
In brief
Overview
According to Engine Manufacturers Association and Western States Petroleum Association, petitioners argue that the case concerns whether section 209(a) of the Clean Air Act preempts the South Coast Air Quality Management District’s fleet purchase rules.
Background and question before the Court
According to Chief Justice Rehnquist, chief Justice Rehnquist opened the argument for No. 02‑1343, Engine Manufacturers Association and Western States Petroleum Association v. South Coast Air Quality Management District.
A Justice asked whether the two sections of the Clean Air Act, enacted at different times, affect preemption.
According to Justice, a Justice clarified that the discussion was not about constitutionality.
A Justice asked whether the fleet rule is preempted.
What each side argues
Petitioner Position
According to Engine Manufacturers Association and Western States Petroleum Association, petitioners argue that section 209(a) of the Clean Air Act preempts the district’s fleet purchase rules.
According to Engine Manufacturers Association and Western States Petroleum Association, petitioners argue the challenge is facial and seeks total preemption of the fleet rules.
According to Engine Manufacturers Association and Western States Petroleum Association, petitioners assert that the fleet rules affect private operators, not just government fleets.
- [1] c428d9baf416611a6d22-r1-62141f9806f3c438.pdf, p. 3
- [2] c428d9baf416611a6d22-r1-62141f9806f3c438.pdf, p. 4
- [3] c428d9baf416611a6d22-r1-62141f9806f3c438.pdf, p. 4
- [4] c428d9baf416611a6d22-r1-62141f9806f3c438.pdf, p. 8
- [5] c428d9baf416611a6d22-r1-62141f9806f3c438.pdf, p. 10
- [6] c428d9baf416611a6d22-r1-62141f9806f3c438.pdf, p. 15
Respondent Position
According to Waxman (Respondents), waxman (Respondents) argue that the fleet purchase rules are modest and apply only to vehicles already commercially available, and therefore are not preempted.
What happened at oral argument
According to Chief Justice Rehnquist, chief Justice Rehnquist announced the start of argument for the case.
According to Justice, justices asked about the timing of the two sections and whether the fleet rule is preempted; one Justice noted the discussion was not about constitutionality.
What the Court decided
Why it matters
Terms to know
No glossary terms are available for this guide.
Primary sources
Read the source materials on the official site or open the immutable repository copy used for this guide.
- c428d9baf416611a6d22-r1-62141f9806f3c438.pdforal argument transcript
Guide generated September 20, 2026. Automated validation accepted this version.