The 2011 Libya action by France, UK, US was supported by a UN resolution authorising enforcement of a no-fly zone - but is there any evidence that the resolution was used as a pretext for the larger act of regime change?
Your question can be broken down into several parts.
- Did the NATO-led coalition deliberately try to topple the Gaddafi regime? I think we can all agree on a "yes" to that one.
- In doing so, did they exceed the mandate of Resolution 1973? I don't think we will get a clear answer on that. The text calls for much more than just a no-fly zone, but it specificially excluded an occupation. Were the special forces teams an occupation force? Some governments which later called 1973 flawed and open-ended had abstained in the UNSC.
- Was there another justification for the NATO-led actions in international law? Again hard to tell, since some of those who argued most passionately against NATO intervention later used military force in their own neighborhoods. Since different cases are never exactly identical, this can be argued at length without a clear answer.