The first lesson is that states still react very differently to violations of humanitarian norms than they do to violations of security-related norms: they are much more likely to assume an aggressive and possibly interventionist posture when it comes to security norms.
The reactions to Syria show this explicitly: there was little talk of outside intervention into the conflict even after tens of thousands of civilians were killed in Mr. Assad’s ruthless response to the uprisings that began in spring 2011. Sincere intervention talk only emerged with the advent of the regime’s use of poison gas in 2013, which violated longstanding norms prohibiting the use of chemical weapons. Though chemical weapons use contains a humanitarian component, it is mostly a security concern: unpunished use of chemical weapons may set a dangerous precedent for further spread and use of such “weapons of mass destruction” (WMD)
another lesson is simply putting a new humanitarian or moral doctrine like R2P in place cannot solve the problem of parochial world politics.