Visa changes for visitors to US

Under the US Visa Waiver Program (VWP), citizens of participating countries are allowed to visit the US without first applying for visas. Each must first fill out the Electronic System for Travel Authorization (ESTA) form online and receive approval before traveling to the US (whereas, in contrast, a visa must be applied for at a consulate). The ESTA application can be found at https://esta.cbp.dhs.gov/esta.
However, under the new Visa Waiver Program Improvement & Terrorist Travel Prevention Act, which went into effect in January of this year, citizens of VWP countries who have visited Iran, Iraq, Sudan or Syria on or after March 1, 2011, or who have dual citizenship with Iran, Iraq, Sudan or Syria must apply for a travel visa at a US consulate and cannot rely on the ESTA for travel approval.