Sense of Past

More revising at the beautiful library. Today's question:

If legal doctrine is just a rationalisation of ad hoc political decisions or a rhetoric of persuasion, what is left of law for normative legal theory to analyse as a structure of doctrine, a conceptual system, a body of principles or a practice on interpretation (Cotterell 2003)?

Take U.S. dept ceiling crises for instance. Is debt ceiling unconstitutional? Will U.S. default on its debts? Whatever the answers, decisions made will be based on political, not legal, ends. Is law just an empty vessel that can be filled with any content?