you are mixing up different meanings for the word "interpret". "Authoritative Interpreting law" (or in general interpreting law) doesn't mean "trying to understand what it means" but means "deciding what it means in practice"

especially if you add a "authoritative" in the front it in legal language means they gave themself the right (i.e. authority) to decide (i.e. interpret) how law should be interpreted, i.e. what the meaning behind the written word is in practice

this is 100% without doubt or question not compatible with any democracy (including the US constitution) and is pretty much one of the default approaches Dictators use to get unchecked authority

It means that in practice (assuming people comply with the EO) means they can do whatever they want as they can just willfully absurdly, but with authority , misinterpret laws. Including to e.g. persecute judges which "step out of line", or members of the senate which don't vote for whatever he wants etc.