I was going to challenge the "irony" statement too.
The rule of law means the sovereign is subject to the words of the law, unless there are agreed exceptions. It's the principle underlying Magna Carta, the English Civil War and the American Declaration of Independence. America's Constitution makes its bedrock source of authority the will of the people, not the inviolable presidency. This is in distinction with the papal notion of top-down divinely ordained authority.
Most wise attorneys and judges know this, even if Jeff Sessions didn't. If the Supreme Court is worth a bean, it will know this.