Whether their specific opinions were correct or not, the idea of an administration determining that the policies of a prior administration are subject to criminal penalties is a major issue. Such action will have a significant impact on the actions of any future administration. All politicians have their own view of the best course of action. Elected officials should not have to worry that their opinions will become crimes because of a shift of a few votes in the next election.
The specific legal basis of whether these prisoners were covered by the Geneva Convention is open to discussion. The prior Administration solicited legal opinions and acted upon them. People from all points of the political spectrum can cite policies and legal opinions that they believe should be declared “illegal”. In the past, Lincoln’s suspension of habeas corpus and Roosevelt’s interment policies were directed at US citizens as so were much more significant to the national principles. They took these actions (right or wrong) based upon their determination of the best interests of the Country.
Subjecting prior policies to prosecution is something that happens in the third world when there is a coup. The proper judgment of an administration’s policies is the next election.