From Talking Points Memo
The deeper offense is that the president has used his pardon power to shortcircuit the investigation of a crime to which he himself was quite likely a party, and to which, his vice president, who controls him, certainly was.
The president's power to pardon is full and unchecked, one of the few such powers given the president in the constitution. Yet here the president has used it to further obstruct justice. In a sense, perhaps we should thank the president for bringing the matter full circle. Began with criminality, ends with it.
A black day for American democracy. One amongst many.