Elizabeth Warren and Cory Booker were among those who protested Saturday in response to President Trump's immigration ban.
The Democratic senators blasted the executive order, signed Friday, which temporarily suspended immigration from seven predominantly Muslim nations and banned refugees.
Warren, a U.S. senator from Massachusetts, denounced the order as "illegal" and "unconstitutional" at Boston's Logan International Airport in front of demonstrators.
"We will make our voices heard all around this world," Warren said. "We have all heard about this order that President Trump has given. It is illegal. It is unconstitutional. It will be overturned."
"An attack on anyone for their religious beliefs is an attack on the very foundation of democracy," she continued. "We will not turn away children, we will not turn away families, we will not turn away people who tried to help Americans. We will not turn away anyone because of their religion."
Near the nation's capitol, the New Jersey senator drove home a similar message Saturday to the crowd at the Washington Dulles International Airport.
"We must stand as witness. We must stand as resistors. We must stand in opposition to what others are trying to do to violate the law, the constitution, and our values," Booker declared.
Members of the Democratic Party are nearly unified in their opposition to Trump's executive order, which sent shock waves to a nation and world still processing its implications. Prominent LGBT rights groups were among those who pronounced the ban as "un-American."
On Saturday night, federal courts issued a temporary stay on the executive order, which declared travelers in transit or in airports at the time of its issuance should not be deported at present, due to the "irreparable harm" such an action might cause. A permanent ruling weighing the constitutionality of the order is awaited.
The White House appeared to back down from a more draconian interpretation of the order Sunday, according to The New York Times. Chief of Staff Reince Priebus said green-card holders could still return to the country. However, he maintained that border agents had "discretionary authority" to detain any suspicious travelers.
Airport protests are scheduled across the country on Sunday.