President Donald Trump's executive order temporarily banning citizens of seven Muslim-majority nations from traveling to the United States has prompted protests online and across the country.

Protests erupted Saturday at airports in New York, Chicago, Minneapolis, Dallas, San Francisco, Portland, Seattle and other cities as word got out that more than 100 people who were "in transit on airplanes" had been denied entry because of the executive order, The Associated Press reported.

>> Read the executive order

Trump's executive order also has caused legal confusion for those who were traveling to the United States when the order was signed, as well as green card holders.

Trump signed the order – which bans citizens of Iraq, Iran, Syria, Sudan, Libya, Somalia and Yemen from traveling the U.S. for 90 days and  suspends the U.S. refugee program for 120 days – in the name of national security, telling an audience at the Pentagon, "We want to ensure that we are not admitting into our country the very threats our soldiers are fighting overseas.”

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Late Saturday, New York U.S. District Judge Ann Donnelly issued an emergency order banning the U.S. from deporting valid visa holders or people with approved refugee applications who have been detained in connection with the ban. In a statement early Sunday, the Department of Homeland Security said, "Prohibited travel will remain prohibited, and the U.S. government retains its right to revoke visas at any time if required for national security or public safety."

White House senior adviser Stephen Miller said that nothing in Donnelly's "order in any way impedes or prevents the implementation of the president's executive order, which remains in full, complete and total effect."

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– The Associated Press contributed to this report.