It largely had been up until 1984, when Chevron v NRDC was decided in a way that yielded a _deference_ that previously didn't exist in determining the scope of executive branch delegation authority via statutory interpretation - e.g., "Can the agency I've tasked with regulating John also regulate the Boy Scouts of America, of which John is a member?" and "If a regulatory agency can regulate John, can it determine for itself that it may also regulate John's best friend Janet just by reinterpreting the statute for itself without input by the executive or congressional branches?"
The intent of the EPA is to regulate things that negatively impact the environment. To use your analogies, the EPA can by the word of law regulate John, and by the intent of law should be able to regulate BSA and Janet if they are operating in ways that negatively impact the environment.
If you limit an entity to only ever operate by the word and not the intent of law, then it's trivial for malicious (more accurately greedy) actors to skirt regulation, because the government will never be able to keep up with the exploitation of loopholes.
Kind of like how the IRS can tax bitcoins, despite cryptocurrencies not being explicitly written into the constitution or tax laws.
That's not how it works. The IRS can tax profits earned from transactions in any medium of exchange (bitcoin or anything else) because Congress has specifically granted them that statutory authority. The EPA does not have blanket authority to regulate anything that might happen to negatively impact the environment. Congress could give them that authority, but has chosen not to do so.
