The legality of arming rebels in Libya?

One of the legal questions that has arisen in the context of the intervention in Libya is the legality of arming the rebel groups fighting the Libyan regime – see for example a recent piece in the Guardian newspaper on this subject.  Attention seems to be focussed on whether or not this would amount to a violation of the arms embargo imposed by the UN Security Council in Resolution 1970.
There is also another, more general, principle of international law that may be violated by the arming of rebels in Libya: the principle of non-intervention.  Recall what the International Court of Justice had to say in the Nicaragua Case in 1986:

The Court considers that in international law, if one State, with a view to the coercion of another State, supports and assists armed bands in that State whose purpose is to overthrow the government of that State, that amounts to an intervention by one State in the internal affairs of the other, whether or not the political objective of the State giving such support and assistance is equally far-reaching … The Court therefore finds that the support given by the United States, up to the end of September 1984, to the military and paramilitary activities of the contras in Nicaragua, by financial support, training and supply of weapons, intelligence and logistic support, constitutes a clear breach of the principle of non-intervention. (paras 241-242)

So would the arming of rebels in Libya also breach this principle?  Does it matter that the rebels are revolting against a regime which has allegedly violated key principles of international human rights and humanitarian law?
Another question that arises is whether a violation of either of these rules (the UN Security Council endorsed arms embargo or the principle of non-intervention) would be justified by UN Security Council Resolution 1973 which authorises the (limited) use of force in Libya.  That would depend on whether or not the arming of rebels was considered “necessary … to protect civilians and civilian populated areas under threat of attack.”  That is a difficult question to answer and various views can be taken.  But it must be asked whether the point of arming rebels is really to protect civilians or is it to facilitate the overthrow of the current regime in Libya?