An 18-year-old US citizen has been held by US Customs and Border Protection and Immigration and Custom Enforcement for over three weeks.

Francisco Erwin Galicia was detained at a CBP checkpoint in Falfurrias, Texas on June 27, said Claudia Galan, his attorney. He was travelling with his brother Marlon, a 17-year-old who was born in Mexico, who was also detained. After two days of detention, Marlon signed a voluntary deportation form and was released to his grandmother.

“I signed because I wanted to talk with my mom,” Marlon told The Dallas Morning News over the phone from Reynosa, Mexico. “Now, we just have to wait and see and hope that they release my brother.”

The brothers were on their way from their home in Edinburg, Texas to a soccer scouting event at Ranger College in North Texas. Travelling with friends, they came upon a CBP checkpoint at around 8pm.

Marlon, who was carrying only his school ID, told News that he had only been through a border checkpoint on school trips. Unlike those times, at this checkpoint he was pressed for travel documents.

His brother Francisco had a Texas ID, however, which can only be obtained with a Social Security Number - a proof of American citizenship. His mother, Sanjuana Galicia, says he was detained because he did not have his US passport.

Ms Galicia says her son was not allowed phone use for the three weeks he was in CBP custody. On Saturday, he was transferred to ICE’s custody, where he’s been allowed to make collect calls.

She told News that she’s presented CBP officers with her son’s birth certificate, along with other documents, including his high school ID, a health insurance, and a congratulatory certificate she was given by hospital staff when he was born.

“They ignored them,” she said. She's now sent the same documents to the ICE agent handling her son's case.

Her son was detained as news of dangerous overcrowding and inhumane treatment in ICE detention centres was met with widespread outrage. The release of photos of people crammed behind chain-link fences, as well as stories from visiting lawmakers, who reported being told by detainees that they were not allowed to wash, among other mistreatments, has sparked support for intervention on the left.

The Trump administration maintains that the detention centres are appropriate for their detainees. Following a highly publicized visit to one centre by vice president Mike Pence, Republicans have stressed that those in custody are not US citizens, emphasising the right's attack on immigration at the southern border. Francisco's case points instead to an outright attack on all people with origins from these nations, regardless of citizen status.

"He’s going on a full month of being wrongfully detained," she said. "He’s a U.S. citizen and he needs to be released now.”

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