Today, the 9th Circuit Court of Appeals continued to block the travel ban. For now, this means that visa holders from the seven affected countries: Iran, Iraq, Libya, Somalia, Sudan and Yemen, can travel to the United States, even if their (otherwise valid) visas were virtually or physically canceled as a result of the ban. Lawful permanent residets and dual nationals from the affected countries and a non-affected country (for example, Iran and Canada dual national) are technically exempt from the ban.
The ban is blocked until the courts decide whether the ban is constitutional. We do not know how long this will take. Visa holders from the affected countries who are currently inside the United States should avoid uncessary travel outside the U.S., and consult with an attorney if travel is absolutely necessary. It is an uncertain time in immigration, and even lawful permanent residents and dual nationals should also consult with an attorney to be aware of their rights before leaving the U.S.