Some facts and my opinions for the masses:
The UN Mandate that France, Britain, the US and allies are enforcing gives authority to participating UN Member States to do the following:
1. Impose a no fly zone in Libyan airspace. This means all aircraft, minus those of participating Member States, Libyan aircraft used for the treatment, resupply and/or evacuation of civilians and civilian airliners evactuation citizens out of the country.
2. Use any and all means necissary to protect civilians from harm, EXCLUDING an occupation force.
3. Facilitate a situation where a ceasefire can be arranged and enforced by the two sides of the conflict.
4. Prevent Mercenary forces from entering Libya and engaging in the conflict.
France and Britain were amoung the first nations to push for a No-Fly zone in the UN security council, leading the charge by submitting a draft resolution. This resolution submitted an idea of a No-Fly zone but not more.
The United States, a little late to the game, submitted a counter draft resolution believing the original one didn't go far enough in protecting civilians.
For something similar, see the peacekeeping force of Somalia in the 90's. US soldiers had to sit back and watch as Islamic Militants ripped UN aid convoys apart because the mandate for the soldiers stationed in Mogadishu only allowed them to fire on rebels if they themselves were being fired at.
I assume the United States didn't want something similar, appearing to lead the charge to protect civilians only to lose face when one of their jets records footage of Libyan tanks demolishing a mosque while the pilot desperately tries to get authority to intervine, and for this to be leaked and plastered all over the news. Hypothetically speaking.
At the moment there is no definitive Commander in charge of the UN mission. The United States put themselves at the forefront but are due to hand over control. Suggestions are that a joint French/British Command could take over, or the NATO command could step in. Norway is refusing to dispatch its committed forces to the UN Mission until a definitive command has been appointed.
The main contentious issue with this UN mission is the fact it isn't clear what consitutes 'protecting civilians from harm'. One might argue that protecting civilians from harm is to destroy a tank convoy attacking a built up city, shelling it indiscriminatly. Another might argue it is better to destroy that tank convoy before it ever reaches the city, despite the fact it may not be clear who or what the tanks intend to target/engage.
The destruction of Air Defence installations is reasonable, in my opinion, as it is part of enforcing a No-Fly zone. If the peace keepers can't safely fly their aircraft into particular sections of Libya, an all encompassing No-Fly zone can't effectively be enforced.
The attacks on Naval bases and command and control centers require a little more reasoning, as I'm unsure how this directly protects civilians from harm. This smells more like decapitating the Libyan loyalist military command, therefore making Rebel operations easier, and that's getting a bit too involved in a civil war for my liking. If we want to actively help the Libyan rebels, we need a clearer mandate allowing us to do so.
Another interesting point to note is that the resolution strictly forbids, using black and white clear language, that an occupation force may not be used. What it fails to do is define what an occupation force is. With clever use of word play and legal language, one can say that putting ground troops to directly assist Libyan Rebels could be a legitimate method of 'protecting civilians from harm' and because the troops are only 'assisting' the rebels it isn't 'technically' an occupation force. Special Forces ground troops can also be quite easily justified, as they are small level combat teams performing very particular roles. SF teams don't take and hold ground in a broader military sense.
My personal view is that the UN needs to get its act together in improving the language used in resolutions to make it clear to what extent nations can use them in support of particular actions. I also have no doubt that various Special Forces troops from the involved nations are currently on the ground performing target aquisition and observation roles, if not directly getting their hands dirty.