Overturning Chevron will not directly affect the former issue. It will not hold that administrative law and rule-making are unconstitutional. It would, however, make it so that in litigation over disputed provisions of federal statutes, the agency's interpretation doesn't have any presumption of correctness. So agencies will still be able to issue rules and form administrative law - but the courts won't give them any deference in how they interpret the statutes that form the basis of those rules and administrative law.

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In the practical world, this is a distinction without a difference.

Let's look at one area of contention, environmental regulation.

Congress passed a law creating the EPA to implement rules for maintaining safe drinking water and air throughout the country. Congress lacked (and still lacks) the TIME and the EXPERTISE to keep pace with evolving science around issues such as lead levels, the presence of plastic nanoparticles, etc. so they leave it to the EPA to adjust rules over time in reaction to evolving science.

One approach taken by giant corporations affected by those EPA rules to combat them is to argue the EPA has no authority to set acceptable limits and that Congress must enact and a President must approve any legislation regulating their business, cuz, you know, FREEDOM. If THIS rationale is held up by the USSC, any new lesson from science about harmful elements found in water would have to be uniquely addressed in new legislation wrangled through a bitterly divided Congress bought and sold by giant corporations, making it VASTLY more difficult to react to evolving science. Sounds pretty extreme, right?

If instead, the USSC intervenes and "clarifies" that Congress ABSOLUTELY has the right to delegate the creation of a rule governing the presence of lead or nanoplastics in water to an agency like the EPA but that agency enjoys zero assumption of being correct in any specific rule established, that simply moves the logjam from the House and Senate to hundreds of courtrooms across all 50 states, producing more chaos as different courts rule differently, generating MORE costs as firms attempt to track and comply with different rulings as they inevitably file lawsuits to reject said rulings. This is effectively saying "Congress has the right to delegate a rule-making authority to an agency but the agency only gets to define a formula y = ax^2 + bx + c but the agency will stil have to fight to set every constant in that formula. That's an infinite amount of variation that can be contested ad nauseum by corporations with billions of dollars at stake and billions they're willing to spend to fight any change.

Okay, as an alternate mental exercise, let's assume a USSC ruling expands / "clarifies" the authority delegated to agencies and says agencies absolutely have the right to designate a DIRECTION of change in a regulated process or substance. For example, Congress not only has the authority to set rules on lead levels, they also have the authority to state that lead levels must go down. Doesn't that take the infinite amount of variation that can trigger lawsuits and at least cut it in half?

No. Because half of infninity is still infinity and if an agency is given no assumption of correctness, corporations can not only argue that a specific LEVEL is arbitrary and capricious without justification, they can also file lawsuits objecting to the MEANS by which the level is measured, arguing the sampling process is inaccurate, subject to partisan interpretation, etc.

The difference between outright delegation of rule-making authority and a "narrower", "more conservative" limit on the presumption of correctness is an intellectal fig leaf the radical conservatives on the Court hand-picked by oligarchs under the guise of the Federalist Society are using to disguise their true intent -- the complete elimination of the mechanisms required in a modern democracy to protect the citizenry from the abuses of economic power held by giant corporations controlling a highly industrialized, high-tech economy.

WTH