Maybe I’m missing something here, but this doesn’t seem as apocalyptic as all that.
Control over regulation-making power isn’t a power grab against the legislature. My understanding is that in the US system, regulatory agencies do not have law-making power, because they are part of the executive, which by definition cannot make laws. Regulations are passed by regulatory agencies based on what they understand the law passed by Congress authorises or prohibits, and what powers the law passed by Congress gives to the regulatory agencies. If Congress decides that the agencies are not properly interpreting the law, or concludes that they don’t like the powers they’ve given to the regulatory agencies, Congress can amend the law as they see fit. So, not a power-grab from Congress.
Nor is it a power-grab from the courts. It’s not trying to exclude the courts. Rather, it’s saying that the DoJ has a centralised power to interpret federal laws for all federal regulatory agencies. If a regulatory agency wants to pass a regulation, the DoJ has the final interpretation, within the executive branch, on whether the federal law authorises the proposed regulation. The federal agency must accept, within the executive branch, the interpretation of the federal law given by the DoJ.
But that doesn’t exclude the courts’ jurisdiction. Anyone who disagrees with a federal regulation and thinks it is not authorised by the law passed by Congress can challenge it in the courts, and the courts have the final say on the interpretation of the federal law. The courts are not bound by the DoJ’s interpretation of the federal law. In fact, that’s exactly what the Supreme Court said in their recent decision overturning Chevron deference: the federal courts have final power to interpret federal laws, not the agencies or the DoJ, so the courts determine if a regulation is within the powers Congress has granted to a regulatory agency.
Whether any of this is good policy is another matter.
(As an aside, I should mention that my views are coloured by the fact that this executive order is similar to how it works in the Canadian federal government. Regulations under statutes are enacted by the federal Cabinet. A regulatory agency or ministry must make the case to the Cabinet why the regulations are needed, and the Cabinet, composed of the PM and all the Cabinet ministers, has the final say. Cabinet can overrule a Minister’s request for regulations. Plus, the federal DoJ has the legal gate-keeper role: the ministry or regulatory agency must satisfy the DoJ that they do have the legal authority for the proposed regulation. Since the Attorney General is the legal adviser to Cabinet, if the DoJ doesn’t think a proposed regulation is authorised by the relevant statute, the AG will advise Cabinet accordingly, and Cabinet won’t pass it. Very simplified summary of a complicated multi-layered process, of course.)