In December 2015, President Obama signed into law a measure placing limited restrictions on certain travelers who had visited Iran, Iraq, Sudan, or Syria on or after March 1, 2011. Two months later, the Obama administration added Libya, Somalia, and Yemen to the list, in what it called an effort to address "the growing threat from foreign terrorist fighters."
The restrictions specifically limited what is known as visa-waiver travel by those who had visited one of the seven countries within the specified time period. People who previously could have entered the United States without a visa were instead required to apply for one if they had traveled to one of the seven countries.
Under the law, dual citizens of visa-waiver countries and Iran, Iraq, Sudan, or Syria could no longer travel to the U.S. without a visa. Dual citizens of Libya, Somalia, and Yemen could, however, still use the visa-waiver program if they hadn't traveled to any of the seven countries after March 2011.
Trump's order is much broader. It bans all citizens from those seven countries from entering the U.S. and leaves green card holders subject to being rescreened after visiting those countries.
