So, my understanding was prior to 1984 if a law was unclear, the courts would get involved and clarify. However, sometimes the courts wanted something that the writers of the law didn't want, and that thing was different from the current congress, which in of itself different from what the president wanted, which even could be different from what the independent executive branch department heads wanted.

This all came to a head with Chevron. In Chevron, anything unclear in a congressional law that applied to a executive branch's mission was left up to the head of that department which in a way was controlled by who the president nominated. In that way, if congress left something vague that meant the courts, congress, and the president all agreed that the head of the particular department in the executive branch got to decide it.

This peace lasted up until Loper in the end of 2024 under Biden. In it, the Supreme court said basically "If something is unclear, it is the courts and not the executive branch" that got to interpret the law. Not wanting to overturn 40 years of regulation, the courts said "anything made under Chevron is still good, but that stops now", most likely since they thought Biden was going to win again and they wanted to take away his power.

Now this EO is saying "No, lol, Loper doesn't mater. No one but the president himself (and DOGE) can interpret the law." At least both Loper and Trump agree that THE REGULATORS can't make new regulations. And because SCOTUS didn't really want that job, and Trump doesn't want to do anything, don't expect any new regulations for the next 4 years.