Eblal Zakzok, an Ohio professor from Syria who is challenging President Trump’s travel ban, stands outside his Columbus home. (Andrew Spear/For The Washington Post)

He was worried about where his son might be, but he tried not to let it show as he texted his daughter 5,000 miles away in Istanbul. "This is not the first time," he tried to reassure her after learning that his son had gone to visit a friend and had not returned.

Eblal Zakzok also had to reassure himself; his son was probably fine, but the anxiety began gnawing at his stomach as he sat safely in the American Midwest. Zakzok's two oldest children were partway through college when the family fled the war in Syria in 2014 — finding asylum in the United States — but his oldest boy and girl, 18 and 21, were left behind in Turkey.

His son's asylum application stalled amid a lengthy vetting process, and his daughter was too old at the time her father was granted asylum to receive the status through him.

Traditionally, U.S. immigration proceedings have allowed for other routes to reunite a family in such circumstances. But Zakzok fears that a reunion might slip out of reach. If President Trump's newest travel ban is enforced, the Zakzok family might be permanently torn apart. A federal judge in Hawaii temporarily blocked much of the latest version of the ban Tuesday, one day before it was set to fully take effect. Early Wednesday, a federal judge in Maryland also blocked the ban, after determining that it was just another "inextricable reanimation of the twice-enjoined Muslim ban."

It has been nine months since Trump first rolled out policies that activists and federal judges branded a "Muslim ban," whose aim was to restrict the travel of people from seven Muslim-majority countries, including the Zakzoks' native Syria. In the intervening months, there have been more than 40 lawsuits, dozens of court hearings and three official policy shifts, the most recent of which imposed an indefinite ban on the citizens of six majority-Muslim countries, as well as on North Koreans and some Venezuelan officials.

Trump talks to reporters Sept. 24 before boarding Air Force One. (Evan Vucci/AP)

Trump has said the evolving measures are necessary to protect national security and prevent would-be terrorists from entering the United States. In announcing a proclamation last month, Trump described his ban as necessary to "protect the security and interests of the United States and its people."

"Making America Safe is my number one priority," Trump wrote last month. "We will not admit those into our country we cannot safely vet."

The administration has vowed to appeal the federal court rulings, as it did for previous versions of the ban, paving the way for a continuing court battle that could — like a previous version — reach the U.S. Supreme Court. Lawyers on both sides say the fight is far from over.

"They've tried to amend each version of it, thinking that will pass legal muster," said Avideh Moussavian, a senior policy attorney at the National Immigration Law Center, noting that the policies all arise from the same flawed baseline. "All of these are fruits of the poisonous tree."

The administration's policies have shifted over time: A few countries have been removed, others added; the government eliminated a specified exception for non-Muslims; and there was a court battle over who would be considered to have a "bona fide" connection to the United States — refugees, it was determined, would not, whereas an American's foreign-born grandmother would.

Trump has intended his newest policy to be sweeping. Some countries would receive specific modifications, but the revision would ban almost all Syrians, Iranians, Libyans, Somalis, Yemenis, Chadians and North Koreans.

The fight over the latest version has unfolded largely behind closed doors. Gone are the dramatic scenes at airports, the swarms of demonstrators and tearful families that came with the early days of the ban. Protests have given way to far less public battles in courtrooms, embassies and consulates against a shifting web of red tape.

It is difficult to calculate how many people would be affected, lawyers say. Considering prior visa patterns, it would be tens of thousands. "It's much easier to account for someone in an airport who is stuck or turned away than for someone who is told to never show up for a consular appointment at all," Moussavian said.

Zakzok is one of those with a pending lawsuit, a case that involves five other plaintiffs, including a Mississippi man whose wife is separated from her sick child, an American, who is receiving medical care in the United States; a New Yorker whose Syrian wife and stepdaughter are stranded in Europe; and a Maryland woman who wants to bring her aging father to live with her family.

It was his case, Zakzok v. Trump, that prompted U.S. District Judge Theodore D. Chuang on Wednesday to determine that the third version of the ban, like previous versions, violated the Constitution for its clear intent to discriminate against Muslims.

"The 'initial' announcement of the Muslim ban, offered repeatedly and explicitly through President Trump's own statements, forcefully and persuasively expressed his purpose in unequivocal terms," Chuang wrote in his 90-page decision, which outlined all of the times Trump has made the intentions of his ban clear in statements and in tweets.

The government offered "no evidence, even in the form of classified information submitted to the Court, showing an intelligence-based terrorism threat justifying a ban on entire nationalities," Chuang wrote.

Omar Jadwat, an attorney for the American Civil Liberties Union, which has participated in the litigation, said plaintiffs in his group have terminal illnesses and want to see their relatives for the last time. There are other people who are trying to start their lives with their families whose spouses are overseas.

"Really basic, fundamental things," Jadwat said. "The whole way that our immigration system works and the arrangements that people have made for their lives, which take these laws into account, have, with the stroke of a pen, been upended."

Zakzok, 47, born to farmers in a rural hamlet of Aleppo, grew up tending sheep and goats but went on to earn a PhD from a British university. His family fled Syria after regime forces arrested him one day on his way to work at the University of Aleppo and held him captive for two weeks, torturing him.

After Zakzok's release, he was invited to the United States to present an engineering paper. He requested asylum. Soon his wife and three youngest children were able to follow.

Zakzok was able to secure a teaching position here, at Ohio State University, with the help of a fellowship program for exiled scholars, and his children settled easily into advanced chemistry and biology classes at the local high school.

But the vetting of his oldest son dragged on for months. And Zakzok had to wait until he had his green card to apply for an immigrant visa for his daughter, which he did as soon as he was able.

Then, Trump was elected after promising on the campaign trail to stop the resettlement of Syrian refugees and limit Muslims' access to the country. Zakzok thought some restrictions would be put in place, but, he said, "I didn't think there would be a law to prevent me from bringing my daughter."

Zakzok has asked that his children not be identified because he fears for their safety. He hopes that the federal court rulings will hold, preserving his ability to bring his children here. But his lawyers have advised that a long battle lies ahead.

"I want him to know that we are like the American people," Zakzok said of Trump. "We like freedom. We share the value of humans, Americans, the free world. We value the safety of our neighbors, of our society. He has nothing to fear from us, from my daughter, my children."

This article has been updated.