When an official at the U.S. passport office in Los Angeles first raised questions about their infant daughter Kessem’s citizenship last spring, Adiel and Roee Kiviti figured that it was just a misunderstanding. After all, they were both U.S. citizens; their names were on her birth certificate; her older brother, Lev—who like Kessem was born in Canada with the help of an egg donor and a gestational surrogate—had no problem obtaining his own U.S. passport when he was born in 2016.

“We sort of naively thought that this is just a big mistake—that once the government realized, perhaps through media, that this was a mistake, it would be sort of rectified, clarified,” Roee told The Daily Beast. “Since then, we’ve started hearing from others who are in similar situations.”

The Kivitis soon realized that the State Department’s refusal to recognize Kessem as a U.S. citizen from birth was no mistake, but the result of a government policy that considers her, as a child born abroad to same-sex parents via assisted reproductive technology, as born “out of wedlock.” The policy effectively invalidates her fathers’ marriage in the eyes of the State Department—and threatens to split the young family apart.

“The scenario that we are now in doesn’t allow us, in the long run, to live in the U.S. as a family,” Adiel told The Daily Beast. “We’re talking about two parents who are American citizens, an older brother who is an American citizen, and a newborn who is not an American citizen. If this is not going to get resolved, we have to leave the United States.”

Now, the Kivitis are taking on the State Department to keep their family together.

In a lawsuit filed in federal district court on Thursday morning, the Kivitis are seeking the recognition of Kessem’s birthright citizenship of the United States—and a judgment declaring the State Department’s policy as both unconstitutional and a violation of federal immigration law.

“This is a fight for marriage equality; this is a fight for the fundamental right to citizenship,” said Aaron Morris, executive director of LGBTQ-focused legal nonprofit Immigration Equality, which filed the suit along with Lambda Legal and the powerhouse firm Morgan, Lewis & Bockius. “And denying a little girl citizenship just because she happens to have two gay dads is intolerable.”

At issue in the complaint, the fourth such case seeking to end the State Department’s policy, is the department’s interpretation of the Immigration and Nationality Act, which sets the legal standard for U.S. birthright citizenship eligibility. Beginning in 2014, the State Department began interpreting the act to mean that a child born abroad “must be biologically related to a U.S. citizen parent,” according to the State Department’s website.

Furthermore, children born abroad via assisted reproductive technology like gestational surrogacy or sperm donation are considered to have been born “out of wedlock,” even if their parents—like the Kivitis—are legally married U.S. citizens.

The hurdles for birthright citizenship eligibility are much higher for children born out of wedlock, and include DNA tests, testimony that the parents are financially able to support the child, and strict parental residency requirements that would disqualify Kessem: Adiel, her biological parent, is a U.S. citizen, but has lived in the United States for four years and ten months, just shy of the required five years. (Both Roee and Adiel were born in Israel, but Roee primarily grew up in California and was naturalized in 2001.)

After The Daily Beast first reported the Kivitis’ story in May, the State Department’s policy faced heavy criticism, ranging from the entire Democratic presidential field and nearly 100 members of Congress to Hollywood celebrities. Sources close to Ivanka Trump told The Daily Beast that even she was “troubled” by the policy at the time.

Nevertheless, the State Department has continued to defend the policy in court. The Kiviti’s case is the fourth such suit filed by Immigration Equality, which already won an early victory in February when a district court judge called the basis for the policy “strained.” But the administration appealed that decision and sought to have another lawsuit thrown out—indicating the State Department’s willingness to take the fight as far as it can, at taxpayer’s expense.

Immigration Equality, Morris said, is more than ready to wage a war of legal attrition.

“The hope is that if they keep losing cases, they will voluntarily take it upon themselves to change their policy,” Morris said. “I’m not sure how many times a district court needs to tell them that they’re contrary to the will of Congress and the law, but we will bring suits until and unless they change the policy.”

But beyond the strategic decision to file four different cases, Morris said, are the individual stories of families who face being separated from their young children due to the State Department’s extra-textual interpretation of immigration law.

“We are determined to have this little girl declared to be a citizen,” Morris said. “If not, she will be undocumented in the United States after this weekend. So the first reason [for filing] really is a very practical, family-based, justice necessity.”

Omar Gonzalez-Pagan, senior attorney at Lambda Legal, agreed, telling The Daily Beast that ultimately, “these cases are about real people and real families.”

“Kids who are being denied their citizenship, and parents who are denied their ability to care for their children in the best way,” Gonzalez-Pagan said. “In every single one of these cases, all that they want is to stand up and protect their children. First and foremost, that’s why we’re bringing multiple cases.”

The State Department’s functional dismissal of the Kivitis’ marriage, Gonzalez-Pagan added, is part of a larger tapestry of discriminatory policies that the Trump administration has crafted, strengthened or defended—combining President Donald Trump’s long-professed hostility towards birthright citizenship with his administration’s track record of dismantling legal protections for LGBT people.

“This administration has shown a disdain to anybody who they view as an ‘other’ or an ‘undesirable,’” Gonzalez-Pagan told The Daily Beast. “They have sought to limit access to citizenship, they have sought to limit immigration, and they have sought to limit the rights of LGBTQ people. I think this is just an area in which those two veins of discrimination in this administration have intwined.”

For the Kivitis, the question of the policy’s intentions is less important than its affect on same-sex parents and their children.

“This is about singling out LGBT Americans—this is about telling gay and lesbian parents, ‘OK, you got marriage, but we know that you’re different. We know that you are not like us, and we’re going to treat you differently,’” Roee said. “Today it’s our family—tomorrow it’s going to be someone else’s family.”

Still, the decision to join a nationwide legal battle to dismantle the policy was not an easy one—particularly with two small children at home.

“It’s not like a trivial decision—like, ‘Hey, let’s go to the courts! And have this legal battle! And go to the media!’ No, no, no. If it was up to us, we would much enjoy having, like, a normal life with a bigger family,” Adiel said. “We have no other choice but to fight for justice for Kessem.”