Under the Visa Waiver Program Improvement and Terrorist Travel Prevention Act of 2015, travelers in the following categories must obtain a visa prior to traveling to the United States as they are no longer eligible to travel under the Visa Waiver Program (VWP):
Nationals of VWP countries who have traveled to or been present in Democratic People's Republic of Korea, Iran, Iraq, Libya, Somalia, Sudan, Syria, or Yemen on or after March 1, 2011 (with limited exceptions for travel for diplomatic or military purposes in the service of a VWP country).
It could not be clearer.