Pardoning Scooter and Obstruction

I have yet to hear any of the pundits talk about this but if Trump is really sending a message, that he will pardon anyone who has lied, how is this not obstruction? Can this simple act not be added to all the others and used against him in a court of law? Is this not an act that just proves all the others? I do not get why everyone is not crying obstruction over this twits latest action.