The Trump administration says they were detained because they had overstayed their visas, but longtime attorneys say that has never been an issue previously for spouses of U.S. citizens.

A British mother holding an infant, a Ukrainian refugee, the wife of a Navy veteran, a German man about to celebrate his first wedding anniversary. These are some of the spouses of U.S. citizens who were recently detained by Immigration and Customs Enforcement at what they thought were going to be routine green card interviews.

There have been several dozen known cases out of San Diego alone, but cases have also been reported in New York City, Cleveland and Utah, according to attorneys and local news reports.

Immigration attorneys told NBC News that this marks an "unprecedented" break in decadeslong practice policy, and that their clients are panicked they could be detained even when they are eligible to become legal permanent residents by law and have no criminal histories.

Jan Joseph Bejar, an immigration attorney in San Diego who recently had a client detained, said if the arrests spread around the country, "It`d be huge. It would be really devastating."

The detentions are one of the latest tactics in President Donald Trump`s policies targeting legal pathways for immigration and increasing scrutiny of green card applicants.

The Trump administration has said in multiple cases that people were detained because they had fallen out of status by overstaying their visas, but longtime attorneys say this has never been an issue and spouses of U.S. citizens looking to obtain green cards were granted exceptions by Congress. The law says that immediate relatives, such as spouses, of U.S. citizens are eligible for green cards even if they were in unlawful immigration status at the time they filed to become legal permanent residents.

"There was a carve-out that was intended for immediate relatives of U.S. citizens, including spouses. This was or is the legal path for them to adjust their status. This is going about doing things ‘the right way,`" said Julia Gelatt, the associate director of the U.S. immigration policy program at the Migration Policy Institute.

She added that because it can take well over a year to go through the entire process, people "could very easily fall out of status right in the process of waiting for that green card through their marriage."

The British woman was released almost a week later and her green card approved, according to NBC San Diego. The Navy veteran`s wife was released on bond, according to the outlet, and must now pursue her case in immigration court. The status of the German man and the Ukrainian refugee are currently unclear. All four had fallen out of status because of visa overstays but were still eligible to become green card holders, according to their attorneys.

Attorneys said the exact number of people affected would be difficult to quantify, but all said many spouses of U.S. citizens seeking green cards could fall into the category of overstaying their visas. There are currently at least hundreds of thousands of people who are at some stage of the green card application process, according to United States Citizenship and Immigration Service data.

Once a green card applicant is detained by ICE, their case goes through the immigration court system, where a prosecutor will argue against the applicant receiving legal status, Bejar said. Because of the yearslong backlog that immigration courts are facing, this will extend valid green card applicants` cases and come at a cost to taxpayers, he said.

USCIS spokesman Matthew J. Tragesser said in a statement to NBC News that apprehensions at its offices "may occur if individuals are identified as having outstanding warrants; being subject to court-issued removal orders; or having committed fraud, crimes, or other violations of immigration law while in the United States."

"The Trump administration has been abundantly clear: aliens must respect our laws or face the consequences," he said. "Overstaying a visa is an immigration law violation that can result in deportation."

ICE said in a statement to NBC San Diego in late November that the agency "is committed to enforcing federal immigration laws through targeted operations that prioritize national security, public safety, and border security."

"Individuals unlawfully present in the United States, including those out of status at federal sites such as USCIS offices, may face arrest, detention, and removal in accordance with U.S. immigration law," its statement said.

Bejar said he had a client married to a U.S. citizen who was detained at a San Diego USCIS office two days before Thanksgiving.

The Mexican immigrant was at the USCIS office with his wife for an interview as part of the green card process. Bejar said the interview had been going well and the officer said he would approve the first part of the couple`s petition. Then ICE agents came and took his client away.

The attorney said his client was brought from Mexico as a young teenager and his parents had overstayed their visa. Now in his early 20s, he recently married a U.S. citizen and sought to adjust his immigration status. As the immediate relative of a U.S. citizen who does not have a criminal record, the man was still eligible for a green card even if he overstayed his visa, according to his attorney.

"When people go in for a green card interview, it`s because they`ve complied with everything else and they`re at the end of the line. In other words, you`re almost there. You`ve gone through the sacrifices of paying for the government fees, for your legal fees," Bejar said.

Bejar said he and other attorneys have been going through their cases to warn applicants in the San Diego area, but their options are limited.

"While there`s nothing in particular that says ICE can`t detain them during that time, it`s always been viewed as a waste of resources, because they are eligible for the benefit of a green card," said Shev Dalal-Dheini, the senior director of government relations at the American Immigration Lawyers Association. "Why would you waste enforcement resources or detention resources on those individuals?"

"Instead of actually picking up violent criminals, like they say they`re doing, they`re picking up people who are following the rules that have been in place for decades," she said.

Courtney Koski, a senior attorney with the Costas Law Firm in the Cleveland, Ohio, area, said she and other attorneys in the Cleveland area have noticed a change in USCIS agents where they are "finding officers scrutinizing and nitpicking every aspect of the case, looking for reasons to deny."

Koski said she recently had a client detained at an interview Nov. 24 as part of the spousal petition process, the step before applying for a green card, even though she was eligible for the benefit and had no criminal history.

The Mexican woman had been in the U.S. for 25 years. Koski said her client had a removal order connected to what she called "a government mistake" where a court scheduled an immigration hearing for the client`s family in July 2004 and then "rescheduled their hearing for April of 2004 without sending my client any type of notice whatsoever."

"This is the reason why my client has a removal order, because the government made a mistake and did not notify her of her hearing date," she said. NBC News could not independently verify the circumstances related to the hearing date.

Her client married a U.S. citizen and was eligible to apply for a green card. Koski said she planned to file to reopen her client`s case once the spousal petition was approved since the approval could help strengthen their case.

"Under the previous administration, people who were being detained generally were considered a threat to national security or threat to public safety, so someone with no criminal history would not have been expected to be detained in an interview like this," she said.

Jeremy Lawer, 33, the woman`s husband, said "the interview was going pretty well, and ICE agents came anyway. We were incredibly shocked."

"She was understandably nervous. But you know, I was like there`s no reason they`re going to deny us. We`ve been living together. We bought a house together," he said.

Lawer said he feels he and his wife have been caught in the "political football" under the Trump administration.

The same day that his wife was detained, he got a letter saying the spousal petition was approved.

Koski has filed to reopen the case and, in the meantime, her client has been moved around to multiple detention centers.

"From my perspective, this all feels kind of like a setup," Lawer said. "Like they had always been intending to arrest her that day."