Yes, but it’s subtle. The mandate of SCOTUS is a check against the other branches of the government to ensure they’re following the Constitution. By passing a Constitutional Amendment, it essentially makes the contents of such inherently constitutional. A Federal law could be (and has been) struck down as being unconstitutional.

I see. I’m probably jumping the gun here, but if such a federal law were to be passed is there something in the Constitution that would disallow it? I suppose it depends on the exact wording and so on?

Generally speaking, a Federal law would only be struck down if its intent or wording specifically violates a clause in the Constitution or its Amendments. So, it really depends on how its worded or what its intent is. I think it's pretty clear that Congress has the Constitutional authority to pass environmental regulations and could extend the EPA's mandates or legislatively codify EPA regulations such that they become law, because they have to do primarily with things which are commerce across state lines and national borders (e.g. where energy originates and where its expended are across borders).

Essentially the same justification for why Congress could create the EPA in the first place allows them to codify any regulations as law or to extend the EPA mandate. What cannot happen is the EPA unilaterally deciding to overreach its mandate, because its taking actions with the force of law but without any check/balance. The Constitution is quite clear that laws are the purview of the Legislative, not the Executive, and the EPA is a function of the Executive.

Yes. A constitutional amendment is constitutional by definition. It’s the very thing SCOTUS is tasked to protect.

Amendments and laws are the same thing, so no. The Constitution can refer to the original laws, or the collection of original laws plus all the new ones.

When Congress passes a law, the law (sometimes referred to as the Constitution) gets amended, hence it is also referred to as an amendment.

Edit: ignore this comment, my information was incorrect!

This is incorrect, at least in the US. A Constitutional Amendment requires the affirmative consent of 3/4s of the states for ratification, it cannot be done unilaterally by the US Congress. The Federal laws are considered the lesser laws and the Constitution the highest law.

There is a big big difference legally in the US between an Amendment and something in the USC

Thanks, got to learn something new today.

You’re conflating constitutional amendments with amendments to congressional bills. They’re very different things.