I have been having a twitter conversation with Roland Paris about the presence of special operations forces [SOF] on the ground in Libya that are from NATO member countries (UK, France) but not part of the NATO effort. Roland suggested that this was essentially a fudge so that NATO folks could claim that NATO has no ground troops. I pushed back, saying that there is more than symbolism here since countries will often not want to put some units under NATO, especially SOF, because they want to retain command and control of these folks.
In Afghanistan, the numbers each country has deployed does not match up neatly with the NATO figures for all kinds of reasons, but especially because countries will not put all of the troops in theater under NATO command. Yes, countries do put some SOF under NATO command (having talked to an Aussie who served as ISAF SOF commander last year, I do know that he had some folks to command), but not all of them. The most obvious instance would, of course, be the SEALs who took out Bin Laden, as they did fly from Afghanistan. These guys and dog were not under NATO command, and I would hazard a guess that while many US SOF have been under NATO command, few of the top echelon folks ever have been. Indeed, one of the messes in the spaghetti chart that is the command structure in Afghanistan has been the separate line from Special Operations Command back in the US to the special operators in Afghanistan. That was supposed to have been simplified under LTG Rodriguez, but it is my semi-informed guess that this was not entirely fixed.
In Bosnia, I know that there were American SOF doing stuff that was not under NATO command (no specifics since this is an unclassified channel), and they were commanded by the senior Americans under their American hats, not their NATO hats. Indeed, the current Dave and Steve project started out pondering the dynamics of dual-hatting--how officers will have to report to two different chains of command and how they manage that. Anyhow, SOF folks in Bosnia clearly operated under the American chain, even though there was no need for optics to confuse the situation since there were at the start 25000 American boots on the ground for all to see.
Anyhow, when NATO sends out a mission to someplace (Bosnia, Kosovo, Macedonia, Afghanistan, Libya), it has to come up with a set of rules that all members to which all members must agree. I am not sure how the OPLAN and such worked for the Libyan operation, but the general standard operating procedure has tended to have countries put only some/most of their troops under NATO command and control and reserve others for national command and control for situations/realities where they expect NATO rules to be less convenient. Or just that they want to have additional discretion about how their folks are used.
In the Libyan case, NATO agreed to deploy air and sea power. Countries wanting to do more would have to do it on their own--France and the UK. NATO has much experience "de-conflicting" the nationally controlled SOF and the multilaterally controlled everyone else. So, they can and do communicate with each other even if legislators back home insist on caveats that limit cooperation between them (for Afghanistan, politicians wanted to draw a distinction between US-led ad hoc Operation Enduring Freedom and the NATO-led, UN-blessed multilateral adventure that is ISAF).
While it is certainly true that is allows NATO to deny having troops on the ground (one of the key joys of SOF is their plausible deniability), I don't think this was the intent of deploying French and British SOF and not NATO SOF. I think at every step of this operation, the French in particular but also the British have shown more enthusiasm than anyone else, so they have been willing to do more than their NATO pals.
While it may look like a dodge to some (like Roland), this is a pattern that has happened again and again even when the rest of NATO was willing to throw in tens of thousands of troops. So, I think I can explain a constant pattern of behavior with a constant--the way NATO and its members always operate--rather than explaining a constant with something that varies in this case--the desire to avoid appearing to have boots on the ground. While there are many differences among the various NATO operations, there has been some significant continuity as well, including having SOF on the ground controlled by their home countries and not under the command of NATO.