In his first week of office, President Donald Trump demonstrated that he’s not backpedaling on his proposed border wall. On January 25, Trump signed an immigration action ordering the construction of a wall to divide the United States and Mexico, emphasizing his plans to have Mexico foot the multi-billion dollar bill. Already, this has caused friction between US and Mexico, with President Enrique Peña Nieto canceling a meeting with Trump. This ongoing dispute will put a wrench in Trump’s wall plans, but it’s not the only thing that will make the wall either ineffective or logistically impossible.

With a cost of upwards of $25 billion, the wall wouldn’t really stop the flow of immigrants from entering the US, because nearly half of all undocumented immigrants overstay their visas, John Oliver explains. Building the wall could only be possible if it bypasses laws like the Safe Drinking Water Act, the Safe Drinking Water Act, and the Native American Graves Protection and Repatriation Act – and it’s with indigenous populations where Trump may find his next hurdle.

Last week, the Tohono O’odham Nation – an autonomous tribe with about 28,000 members living along the US-Mexico border – released a statement denouncing the wall. It invited Trump to visit the reservation, and said it should be part of the conversation.

“The executive order signed yesterday was done without consultation with the Nation or many other border communities,” the statement read. “As a first responder on the border, the Nation invites the new President to visit so that in depth discussions can be held on the impacts of such actions. In the interim, the Nation will continue to do its part to ensure the security of the U.S. border.”

Whether or not Trump takes them up on the offer, the tribe won’t allow him to build a wall on the 75 miles of the reservation that runs along the border. “It cuts through our ancestral land, and it divides families that have been able to go back and forth freely since before the border line was drawn,” Tohono O’odham member Bradley Moreno told The Guardian. “Border Patrol is a way of life for us.” The indigenous community’s land historically stretched from Sonora, Mexico to north of Phoenix. Members still live on both sides of the border.

The militarized border – as well as the steel barrier that runs along the reservation – has already inconvenienced the members’ lives and interfered with its customs. The tribe reports that Border Patrol agents have deported members of the tribe who were “simply traveling through their traditional lands, practicing migratory traditions essential to their religion, economy, and culture.” A border wall would further disrupt their lives. “It’s going to affect our sacred lands,” Moreno added. “It’s going to affect our ceremonial sites. It’s going to affect the environment. We have wildlife, and they have their own patterns of migration. There are just so many things that are wrong with this. The whole idea behind it is just racist.”

In an interview with KJZZ last year, tribal vice-chairman Verlon Jose made it clear that the Tohono O’odham Nation will fight to protect their culture and land. “Over my dead body will a wall be built,” he said. “I don’t wish to die but I do wish to work together with people so we can truly protect the homeland of this place they call the United States of America. Not only for our people but for the American people.”