Thousands of demonstrators rallied outside the White House and in cities nationwide Sunday to protest President Trump’s immigration ban as the executive order continued to halt travel in some locations, despite being weakened by federal judges overnight and having its constitutionality called into question as rulings spilled into Sunday.

In addition to Washington, large protests took place in New York, Philadelphia, Boston and Atlanta, as well as at airports in dozens of cities, including at Dulles International Airport in Northern Virginia, where demonstrators created cheering sections for arriving refugees.

In Washington, swarms of protesters had amassed in front of the White House by 1 p.m. The crowd proceeded to the nearby Trump International Hotel and Capitol building and later made its way back toward the White House, shutting down Pennsylvania Avenue.

Demonstrators cycled through a variety of chants and wielded poster boards bearing messages such as “Islamophobia is un-American” and “Dissent is patriotic.”

“Say it loud, say it clear, refugees are welcome here! No hate! No fear! Refugees are welcome here!” they chanted.

“No justice! No peace! No justice! No peace!”

The tone vacillated between forceful and unifying, as protesters alternately chanted “Shame!” and partook in renditions of “America the Beautiful” and “This Land is Your Land.” By evening, an impromptu Catholic Mass brought hundreds more to bordering Lafayette Square to resist Trump’s order.

George Formukong, a police officer in the District, came to the rally with his family still wearing their dress clothes from church.

They flew back from their native Cameroon on Saturday to learn that other travelers were being denied entry.

“Because our country was not on the list, we were able to travel,” Formukong said. “Everyone is an immigrant here. We should have equal treatment.”

Also among the protesters was Shohreh Rahnama, of Bethesda, Md., whose 5-year-old son was detained for several hours at Dulles Airport after a flight from Istanbul on Saturday night.

Artiman Jalali was born in the United States and has dual citizenship with Iran. He was traveling back from visiting relatives with his cousin, 25-year-old Aida Mohammadi, a University of Maryland student and a green-card holder.

Rahnama said she waited for hours at the airport with friends and family and a growing crowd of strangers who came to support them and others whose loved ones were detained. Artiman and Mohammadi were finally released around midnight. “He was hungry and he was thirsty, and I could not see him,” she said.

“How can a 5-year-old be banned? Just because his parents are Iranian? We are American, too,” she said. “I almost died in that airport. I can say it was the worst day of my life.”

Sunday morning, she brought her son and other family members to join the protest at Trump’s doorstep. She wanted to send a message.

“I am here to say: ‘You cannot do this. You are our servant. The people elected you,’ ” she said. “Other countries are thirsty for the rights we have in America. We can’t become a dictatorship.”

Trump reaffirmed the order in a statement Sunday, saying it did not constitute a “Muslim ban.” He compared it to President Barack Obama’s 2011 action blocking visas for Iraqi refugees for six months. Trump said he intends to prioritize persecuted Christians in the Middle East for admission as refugees, and in a weekend television interview, former New York mayor Rudolph W. Giuliani said Trump wanted a “Muslim ban” and asked him to assemble a commission with the knowledge to institute one “legally.”

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The ban bars entry into the United States from seven predominantly Muslim countries. Despite a federal judge’s ruling late Saturday and similar court decisions with varying degrees of power, the Department of Homeland Security issued a statement Sunday that it would continue to implement order.

Demonstrators also gathered Sunday morning at the Capitol to protest Betsy DeVos, Trump’s nominee for education secretary. At least one demonstrator was equipped for both protests, carrying a poster that addressed one of the issues on each side.

Meanwhile Sunday afternoon, several U.S. congressmen squared off with authorities at Dulles Airport to try to get information on the identities and status of detainees.

Democratic Reps. Don Beyer and Gerald E. Connolly, both of Virginia, and Jamie B. Raskin of Maryland, were followed by a crowd to a hallway that led toward internal offices where they believed customs officials were located.

Squeezed up against the narrow hallway, Connolly pressed an airport police officer to get a Customs and Border Protection official to meet with the group.

“Are people being detained?” he asked the officer, John Damskey, a member of the Metropolitan Washington Airports Authority police. “How can you enforce the law if you’re not enforcing a judge’s order?”

Connolly was handed a cellphone. On the line was a Customs and Border Protection congressional affairs official. Connolly asked for information on possible detainees, including those traveling on a flight from Turkey from which airline customers reported that some passengers had been pulled. No one on site from CBP would meet with the congressmen.

“That is unacceptable. It is our understanding you are detaining people. . . . Our understanding is you have not followed that order,” Connolly said.

Connolly said that a lawyer for one of his constituents was allowed to communicate with his client late Saturday night and that the person was released.

Virginia immigration attorney Sharifa Abbasi was among the lawyers on hand at Dulles on Sunday pressing for information on passengers potentially detained under the executive order.

Abbasi also asked a CBP agent for information on who was currently detained at the airport. She pointed to an order from U.S. District Judge Leonie Brinkema in Alexandria that mandated that lawyers must have access to green-card holders detained under Trump’s measure.

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Abbasi said she was turned away.

“They won’t give us any information,” she said.

Inside the airport, hundreds of peaceful demonstrators sang the national anthem and created a cheering gantlet for travelers emerging from customs.

The crowd shouted “Let them in!” and “Welcome!” as passengers, including some from majority-Muslim countries, rolled their suitcases through gray doors and into a section of the airport that had become a makeshift law office and civics classroom.

“My kids go to school with people from everywhere,” said Sasha Moreno, of Reston, Va., whose 6-year-old daughter drew a little, red Statue of Liberty on poster board along with the message: “Welcome to America.”

Her daughter’s kindergarten class includes many students from Sudan, one of the countries targeted by Trump’s order, which has created a sense of anxiety in Moreno’s own family. The idea that her daughter’s friends’ grandparents would be barred from visiting the United States just because of who they are is unacceptable, and she wants her children to know that’s not what America stands for, Moreno said.

“There are lots of Muslim students at her school. Hearing this stuff going on is really confusing” to them, Moreno said. “We like the idea of them having friends from everywhere.”

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Georgia Warner brought her nearly 3-month-old son to Dulles on Sunday, along with a sign that said “Raising my son to tear down your wall #NoBanNoWall.”

He was born on Election Day.

Warner is an 11th grade American history teacher in the District nearing the end of her maternity leave.

“There might not be a better time in my lifetime to teach the U.S. Constitution and U.S. history,” she said. Her message to visitors from around the world: “There are still people who will stand by them and defend their rights.”

Her husband, Chris Miller, said America’s “capacity for inclusiveness” deserves to be protected.

“It’s my job as a patriotic American to stand up for American values,” Miller said as he fed and burped his infant. The family also was headed to protest at the White House.

"My oath didn't end when my enlistment did," said Lee Carter, a demonstrator who served in the Marines and is running for state office in Virginia. He carried an oversized florescent green declaration: "I, Lee Carter, do solemnly affirm that I will support and defend the Constitution of the United States against all enemies, foreign and domestic #nevertrump #resist."

For some, the demonstrations were particularly personal.

Amira Hassan, 26, remembered the excitement she felt when she flew into John F. Kennedy International Airport with her family as a refu­gee from Somalia in 2001.

Hassan is graduate student in public administration at American University and a naturalized citizen. Since the Sept. 11, 2001, terrorist attacks, she said, she has watched the rise of Islamophobia as her family built a life in the U.S.

“It’s hard not to feel terrified and angry and sad and heartbroken,” she said.

Perry Stein contributed to this report.