After months of court battles, President Donald Trump's travel ban went into effect Thursday night.
Travelers from six Muslim-majority countries with links to terrorism have to meet certain requirements before they can enter the U.S. The countries affected include Iran, Libya, Somalia, Sudan, Syria and Yemen.
The president says he's simply acting to protect Americans from possible terrorism.
"(The) American public could have legitimate concerns about their safety when we open our doors," said Heather Nauert, a State Department spokesperson.
There was no chaos at airports, which remained calm overall, although protestors gathered at Los Angeles International Airport.
"We don't want to be living in a society where people are discriminated against," said protestor Keith James.
"They're trying to find a way into this arena of suppressing Muslim rights, so if they are successful with these countries, more countries will get added," warned Ameena Qazi of the National Lawyers Guild.
Protestors also spoke out at Union Square in New York. Widat Hassan, a Yemeni-American, said her family members are stuck in a war zone.
"I've been very mentally and emotionally drained from all this for a while," she said.
On Monday, the U.S. Supreme Court in a unanimous decision reinstated practically all of the revised travel ban -- overturning lower court rulings that critics said amounted to liberal overreach.
The high court said travelers who could prove a "bona fide relationship" with a U.S. person or entity could enter the country.
The State Department this week said those personal relationships include a parent, spouse, son, daughter, son-in-law, daughter-in-law, sibling or fiancé/fiancée already in the United States.
The president's initial travel ban in January surprised travelers and fueled widespread protests.
The revised version could lead to a new round of court battles. Already the state of Hawaii filed an emergency motion, requesting that a federal judge provide more clarification on what exactly counts as a personal relationship.
The Supreme Court is scheduled to consider the overall ban in October.