For the United States, international law has been used as a means to put forth legal arguments that advocate for the protection of Ukraine's sovereignty. On Saturday, President Obama accused Russia of a "breach of international law" and the violation of Ukraine's sovereignty, and said that "there will be costs" if Russia continues with its military intervention in the Crimea region. In The Uses and Limits of International Law, Stanley Hoffmann discusses how international law can be useful for "protection or enhancement of a position," which so far has proven to be crucial in the current conflict. On Sunday, the Secretary-General of NATO, Anders Fogh Rasmussen, said that Russia was violating the principles of the United Nations Charter and was threatening stability in Europe. The Ukraine has ties with NATO but since it is not a member, Article 5 of NATO (which states that an attack against one member is the same as an attack against all) cannot be invoked (See this article). This clause is a powerful diplomatic tool. Seven leaders have boycotted the G8 summit which is to be held in Russia, which is the start of economic and political isolation for Russia. These methods are meant to isolate Russia using soft power. States are making their interests clear to the Russian Federation.