The travel ban affecting citizens of Iran, Libya, North Korea, Somalia, Syria, Venezuela, and Yemen has been in full effect since December 2017, but waivers of the ban necessitated by, e.g., undue hardship or the absence of national security concerns, have been rare. According to a March 2018 letter from the Department of State to Senator Chris Van Hollen, consulates had by February 15, 2018, approved only 2 waivers, and had rejected 6,282.
More recently the State Department claimed that as of May 31, 2018, consulates had “cleared for waivers” 768 travel ban affected visa applicants, of which an unspecified “many” had been issued visas. It is very common for U.S. consulates to invoke “administrative review” of visa applications lasting months, and which often result in eventual visa refusal. The State Department is permitted to refuse a visa application for any reason, without specific explanation, and without judicial or other rights to appeal.
The U.S. Supreme Court has heard oral arguments in an appeal seeking to invalidate the travel ban on constitutional grounds, and is expected to issue a decision by the end of June.