The normal and plain reading of Article II section 2 clause 1 of the US constitution grants the president the power to grant repreives (reduction or elimination of punishment) or Pardons for offenses against the United States. Nowhere is it stated or implied that these can be preemptive. In fact when taken with the principle of innocent until proven guilty, there is no offense to be pardoned until AFTER a conviction. I dont believe it was intended to be preemptive and see no grant of such power.
@Phil Well, key to this is whether an offense is the action or the crime.
If I break a federal law but I'm not charged, did I or did I not commit an offense against the United States?
Another issue with your post is, do you mean preemptive to the action or preemptive to charging/conviction? I'm not sure which you were saying, and it makes a difference.
