Our legal system is a continuation of the English common law system of the American colonies.
The magna carta falls within English legal history and is widely viewed as the first step in regulating the behavior of the king.
This supreme court ruling seems to allow the President to break the law.
It's my own comparison, but I think it's quite good.
I could also say that they've made the presidency into a dictatorship (in the Roman usage of the word). That's actually unfair to dictators, since they could be prosicuted when they left office.