Well, if your first sentence is correct, then I think we have a major constitutional crisis, because I just described what amounts to an effective repeal of the law.

To extend the idea further: What's to stop the president from changing any deadline or date in any law? Almost every bill passed by Congress contains a line that reads "this act is to be effective on date X". If the president can waive this it will, then we have not only just given him a line-item veto, we have given him a line item repeal.

If the case is that the only impediment to the executive branch unilaterally rewriting laws is politics, then we don't really live in a representative government with checks and balances, we live in a term limited elected dictatorship.

It's my opinion that the current president is firmly in unconstitutional territory.