Climate change is the world’s greatest environmental threat. It is also increasingly understood as a threat to domestic and international peace and security – recognized by the Department of Defense as a “threat multiplier,” by Secretary of State John Kerry as “perhaps the world’s most fearsome weapon of mass destruction,” and by President Obama, in an address to graduates of the United States Military Academy, as “a creeping national security crisis.” The Supreme Court’s temporary blocking of the Clean Power Plan highlights the Federal-State divide over how to address climate change, but because of its national security dimension, climate change also raises unique separation of powers issues between the president and Congress with regard to how the military can respond.