Briefly: Trial by jury and rights of the accused; Confrontation Clause, speedy trial, public trial, right to counsel
In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed, which district shall have been previously ascertained by law, and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have compulsory process for obtaining witnesses in his favor, and to have the Assistance of Counsel for his defence.
Diane Feinstein has proposed legislation "to ensure that drone strikes are carried out in a manner consistent with our values, and the proposal to create an analogue of the Foreign Intelligence Surveillance Court to review the conduct of such strikes".
First, whose values will be consistent with drone strikes. If she's talking about the federal government's values, I think we're all in a lot of trouble.
Second, this amounts to nothing more than a secret court making secret determinations without the need to shoulder the onerous burden of due process.