This gets into the seam between law and regulatory authority.
I happen to believe that, no matter which party is in the executive office, that congress has relinquished too much power to regulatory authority. The late Robert Byrd agreed with me.
Now it starts with the language of the laws as they are passed - many leave themselves very open to later modification by regulation. As an example, I write reports to comply with the 1973 Clean Water Act. The requirements change every few years...and the EPA actually re-certifies the states every 10 years, with a new list of requirements that were unheard of in 1973. The law was written in a manner that allows this, which I think is a disservice by congress..
Same with ACA...the employer mandate was supposed to be in 2014, now its delayed by HHS action. Was that the intent of the congress that passed this just 4 years ago? Probably not. The law should have explicitly prohibited such modification.
(BTW my objections to the Clean Water Act are nuanced, and its a very long story, but the way municipalities react to the regulations are based in what is defensible in court, and creates a system where hundreds of smaller property owners are required to do measures in an unorganized way, and makes it unfeasible to pool resources and create large scale wetlands, etc. Short story - instead of the new business district in your town having a 20 acre wetland at its downstream end, each new business will have a pathetically small and ineffective 'bioswale' behind the building...and the methodology of enforcement steers us towards that reality).