The legislature has already long since punted regulation of most things to the executive. The Code of Federal Regulations is a lot larger and lengthier than the United States Code. That includes environmental regulations: the EPA is an executive agency.

If your response is that the above is a bad idea, I agree; I think the legislature should be prevented (by Constitutional amendment, if necessary) from punting regulation to the executive. Anything that has the force of law--and regulations issued by executive agencies do--should have to go through the Constitutional process to create a law. But that's not how things are currently done.