During an ongoing insurgency in Syria, Turkey has already used military force against Syrian military targets inside Syria. Was this use of force by Turkey permissible under international law? If NATO engages in similar military force or more extensive armed force as a regional organization, will NATO’s conduct be permissible under international law as part of collective self-defense or as a “regional action” under the Charter? U.S. military have been deployed to Jordan. If the United Sates engages in the use of force in Syria under certain future scenarios, especially (1) to destroy chemical and biological weapons and (2) to support the government of the legitimate representatives of the Syrian people, will such conduct be permissible under international law? These and related questions are explored in the essay.