It’s well established that the American president can issue preemptive pardons for federal crimes that have already been committed but not yet prosecuted or tried. (If you’re not aware of this, please see any of the zillions of other threads here on this topic.) The president also has the power to commute sentences; can this power also be exercised preemptively?
Consider the following scenario: a president becomes aware that someone has committed a crime and believes that this person is guilty but will receive an overly harsh sentence. (Perhaps the crime is a capital offence and the president is opposed on principle to the death penalty.) However, the sentencing (or maybe even the conviction itself) is not expected to occur until after the president leaves office. Can the president impose an upper bound on the possible sentence by exercising the power of commutation? For instance, could the president rule out the death penalty before a judge even imposes one, or decree that a yet-to-be-issued prison sentence cannot exceed a certain number of years?