Nearly 11 million illegal immigrants now live in the United States, and more than half of those immigrants are from Mexico, according to a new report by the Pew Hispanic Center.

Eleanor Eisenberg, executive director of the ACLU of Arizona, acknowledges that while the group has a constitutional right to peacefully assemble she sees a potential for violence.

"Assuming that the organizers of the project have the best of intentions for making this a peaceful event, they are not going to be able to control the people who are coming from white supremacist or other hateful organizations," Eisenberg said.

The ACLU has received threats, some from people who have identified themselves as volunteers with the Minuteman Project, Eisenberg said.

Cochise County Sheriff's Department spokeswoman Carol Capas said organizers have assured law officers the protest would be peaceful. The department is ready to respond but for now is planning business as usual, she said.

The group's mission statement said volunteers must follow a "no contact, no engagement policy," though they may, in most places, carry a firearm for self-defense under Arizona law.

"Any volunteer who even hints at illegal activity will be quickly ostracized from the mission and will be reported to law enforcement," the statement states.

Eisenberg said the ACLU will monitor the situation. She said she's spoken with law enforcement officers, and "they seem to be ready to deal with this situation."

"These people are going to be able to carry a sidearm under Arizona law," she said. "We are greatly concerned."

Minuteman Project co-organizer Chris Simcox said the group will remain within the law.

"How else do we make our point without strictly adhering to the laws of the state of Arizona?" asked Simcox, publisher, editor and owner the Tombstone Tumbleweed newspaper and founder of the Civil Homeland Defense Group.

"It's a symbolic political protest," Simcox said. "We demand our elected officials work for Americans first by protecting our border."

UFIRE co-chairman Russell Sias, who recently returned from helping to prepare for the volunteers who will be arriving in Tombstone soon, said: "I find it absolutely amazing what's going on."

"I've watched buses pull up on the highway. . . . They drop off two to three busloads at a time," he said. "They sit there until it gets dark, then they walk across the border."

Sias said a few businesses have told the minutemen they're not welcome, but he sees strong support from many in the area.