Ron Radosh reviews the handling of the underpants bomber and reports in detail why historian Martin Sklar thinks Holder can and should be impeached. 

 Sklar... argue[s] that the decision for a civilian trial disarms our country and objectively arms our enemies. Ignoring this outcome, he argues, is malfeasance of duty, "a betrayal of the public trust and a violation of the constitutional oath of office."  He then makes this historical analogy:

The circumstances at present are strongly analogous to those of the Republican Party and pro-Union Democrats versus Andrew Johnson and the resurgent Secessionist/pro-slavery Democrats of 1866-68, the latter seeking to turn their defeat in war into victory via propaganda, demoralizing politics and terror, and constitutional usurpation. ...

Eric Holder also claimed that he had not discussed the decision with the President before announcing it publicly, and President Obama confirmed his account. Sklar argues that "this could be considered a serious malfeasance on the part of the President, a not minor breach of his oath of office to preserve, protect and defend the Constitution, and a serious deficiency in a Commander-in-Chief, particularly in war time." Moreover, Holder is an executive officer appointed by and removable at the will of the President, and hence subject to Obama's authority. Legally, therefore, Sklar argues that if Obama does not countermand Holder's decision, or remove him from office, the decision for civilian trial is as much his as the President's.