In diplomacy, red lines are problematic. While they are needed to signal resolve, they can also invite trouble. "Red lines often become red carpets," showing that what governments do to challenge their adversaries and test their credibility turns into an indication of how far they can go without inviting retaliation.
In some cases, however, there can be no room for doubt. The prospect of Syrian use of chemical weapons is one such instance. The world must make clear that any such action by the Damascus government will trigger strong multilateral action. Some lines must not be crossed.
In recent weeks, the United States has ratcheted up international attention on the prospect of the use of chemical weapons by Syria. U.S. Defense Secretary Leon Panetta has said intelligence "raises serious concerns that this is being considered."