Continuing its energetic campaign to narrow the power of federal regulatory agencies, the Supreme Court’s conservative majority on Thursday stripped the Environmental Protection Agency of authority to write industry-wide curbs on emission of air pollution by electricity-generating plants.

Without a specific new grant of authority from Congress, the Court’s 6-to-3 decision declared, EPA must mainly limit itself to restricting carbon emissions, one energy plant at a time.

The decision appeared to be even more sweeping and with potentially greater impact than the Court’s decision last January nullifying the Biden Administration’s mandate of vaccines, testing or mask-wearing to prevent the coronavirus from spreading at major private business firms across the nation.

The new ruling dealt with the problem of global warming that results from the rise of poisonous gases into the world’s atmosphere.  Electricity-generating plants, along with car and truck exhaust pipes, are the main sources of air pollution in the nation.

The new decision declared that the Obama Administration had no authority, in response to the Paris agreement on climate change policy, to adopt a so-called “Clean Power Plan” in 2015, and it ruled that the Biden Administration could not revive that plan or anything as broad as that Plan unless Congress explicitly writes a new law granting such authority.

The ruling was based on a recently-developed, court-fashioned approach on how to interpret federal regulatory laws – the so-called “major rules doctrine.”  The idea is that, if a federal Executive Branch agency or an independent regulatory agency wants to adopt a policy with sweeping economic, social or political impact, it can only do so if Congress – in very clear and specific legislation – grants that power.

The doctrine is said to be an application of the basic theory that the powers of the national government are separated constitutionally between three branches, and each branch must largely stay in its own domain.  But, for conservative scholars, judges and lawyers, it is manifestation of a long-held suspicion of the power of so-called “unelected bureaucrats” operating in a constitutionally illicit “fourth branch of government.”

In the Clean Power Plan, which never went into effect, the EPA seven years ago decided that the best way to achieve a reduction of air pollution from energy plants was to require shifting of generating capacity from high-polluting plants – those, for example, that burn coal or oil – to lower-polluting plants – those that burn natural gas or run on wind or solar power.

The Biden Administration was in the midst of studying what new plan to adopt after the Trump Administration had scuttled the Clean Powe Plan.  President Biden’s lawyers had urged the Court not to rule on the legality of the Clean Power Plan approach until after the new review had been completed.  The Court declined to wait.

The Court’s ruling on EPA’s power was the next-to-last decision the Court issued as it prepared to finish its current term later in the day.

In the final ruling, the Court decided that the Biden Administration did not violate federal immigration law when it chose to abandon the former Trump Administration’s “return to Mexico” policy, sending to Mexico refugees who entered the U.S. illegally but seeking asylum.  They were to stay in Mexico pending rulings on whether they could enter.  Chief Justice Roberts again wrote for a 6-to-3 majority – made up of a different combination of Justices than in a major ruling on air pollution earlier in the day — siding with the Biden policy.  The case was sent back to lower courts for further study.