Chris Hanley from TNS opinion and James Downes from Parliament Street discuss the ramifications surrounding ISIS, drawing on recent polling data from TNS opinion, Pew and YouGov. The article then looks at four core areas in the legitimacy to intervene, investigating authorisation from the UN Security Council, Humanitarian Intervention, intervention by recipient states and the right to self-defence. The article then concludes by outlining complications surrounding contemporary international law and the different foreign policy approaches that the two sides of the Transatlantic partnership currently have.