Both presidential candidates George W Bush and Barack Obama said that the USA should not be the worlds policeman or engage in foreign nation building. In doing so they paid lip service to the US constitution. Here another potential presidential candidate, Rand Paul, says the words that must be popular (why else would they keep saying it). However I doubt he will use his senate position to argue that the current president be impeached. That would hurt his popularity. It is however the only way for congress to assert that it has ultimate authority in such matters.
My view on the Libyan no fly zone is layered. In the first instance it is nothing to do with Australia so we should in essence ignore it. From a US constitutional perspective it seems clear that the UN is seen by many as having more moral and practical authority than congress. From a military perspective it seems mad to enforce a stalemate and if your going to make yourself an enemy of the Libyan government you should make the destruction of the Libyan government a core military objective. I don’t see any shining lights in this fiasco.