Pursuant to the Clean Air Act Amendments of 1970,
EPA had issued a national ambient air quality standard (NAAQS) that
required substantial reductions in SO2 emissions.
Under Clean Air Act §110, when a NAAQS is
approved, the States are required to submit State Implementation Plans
(SIPs) detailing how they will comply with the new NAAQS.
Missouri submitted a SIP, which was approved by EPA. Union
Electric sued to stop the SIP.
Union Electric argued that EPA should not have approved
the SIP because it required electric utilities to meet a technologically
EPA argued that they had no power to reject a SIP on
economic or technological feasibility grounds.
The US Supreme Court found for EPA.
The US Supreme Court found that when Congress passed the Clean
Air Act, they did not intend for the EPA to consider economic or
technological feasibility grounds.
In fact, the NAAQSs are designed to force the
development of new technologies.
"The State has virtually absolute power in
allocating emission limitations so long as the national standards are
So basically, the Court said that if the State
government wants to make an impossible standard and ends up losing the
entire industry because no one can meet the standard, that's their
problem, and the EPA can't tell them no.
In fact, §110 specifically limits the reasons
EPA can decline to approve a SIP, so even if EPA wanted to reject it
due to costs, they couldn't.
Under §123, EPA does impose some limitations on
the kind of controls that a State can employ (mostly involving ways to
cheat and get around the regulations).
After this case was decided, Union Electric miraculously
found some way to meet the new standard without going out of business.