I remember reading here that the regime itself claimed that it did not have authority in the law to do this.
The ACA has turned out to be the outrageous disaster that many Republicans predicted it would be (at least publicly), so the Obama administration is basically -- with no authority at all -- stripping the original law of one provision after another. But nobody is going to complain about it because this is basically the equivalent of an innocent man being convicted unjustly in a court of law ... without a judge ever enforcing the sentence.