Actually it's according to law, at the time the constitution was written which did NOT give the president the broad immunity the current USSC gave him.
The constitution was written to demand punishment for the crime, and any laws written in contravention to the demand for punishment, such as the presidential immunity decision, go against the constitution, and are therefore VOID as unconstitutional.
The current conservative court has to interpret that clause, as they have every constitutional clause, according to the clear text, and meaning at the time it was written.