How much should the community of nations interfere in regional political affairs? The present strife in Syria has been condemned by a UN General Assembly resolution (document A/66/L.57; passed 133 to 12, with 31 abstentions). But the resolutions has no binding legal sanctions. Past resolutions seeking peace elsewhere in the Middle East have too often done nothing.
What might the UN General Assembly have done in the case of the American Civil War? The Confederate States of America ultimately was re-amalgamated into the Union, but after horrible losses of perhaps a million dead overall. Efforts to trigger European intervention & mediation had little impact.
The United Nations Charter prohibits member nations from aggressive attacks against others. The idea is good, but many such attacks have taken place since WWII. Chapter VII of the UN Charter gives the Security Council the possibility of imposing military power "to maintain or restore international peace and security." But any of the UN Security Council's five unelected members (China, France, Russia, UK, USA) can veto intervention. In the case of Syria, both Russia & China have strongly resisted intervention. But judging from past unlawful interference elsewhere by big military powers, (which remains largely unpunished), surely surreptitious destabilization is underway now.