No person is above the law. Presidents merely get a stay on civil and criminal prosecutions.
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Presidents get Impeachment, Conviction, and Removal in office. Out of office they should be immune.
Else no one will run for President ever again, since someone somewhere will charge them with some crime while in office.
This also opens the door for the World Court to step in and extradite a former President for some crime. Some President; Some Senator; Some ordinary citizen; Any One can be found guilty of some law existing or retroactive.
Correct
Presidents are immune from prosecution while in office. That immunity is kept in check by the Impeachment process. If they survive the Impeachment process their immunity is intact.