Turkey – notwithstanding its official denials – has shown itself extremely reluctant to designate the Islamic State (ISIS) a terrorist organization, and that reluctance has hampered efforts to bring ISIS suspects to justice. Ankara has frozen the assets of ISIS but continues to stop short of officially labeling it a terrorist group. In view of the fact that ISIS has used Turkish territory as a transit route into Syria and Iraq and has placed sleeper cells in dozens of Turkish cities, Ankara would be well advised to designate the group a terrorist organization.