A legal claim filed today says the Tucson Police Department acted improperly in a traffic stop last fall that drew dozens of protestors.

The American Civil Liberties Union filed the claim, which is the first step in suing a government. At issue is a traffic stop of two immigrants that sparked an impromptu effort to stop Border Patrol agents from taking the driver and passenger.

This is the second legal challenge the ACLU has filed against Arizona police departments since SB 1070's so-called "show me your papers" provision took effect in September 2012. Part of the state's tough immigration law, it requires that police try to check the legal status of those stopped for other reasons. The first claim was filed last November against the South Tucson Police Department. Negotiations continue between the city and the police department.

In the case that prompted today's claim, Agustin Reyes and Arturo Robles were stopped by on Oct. 8 by a TPD officer near Southside Presbyterian Church, 317 W. 23rd St., a church with a long history of immigration-related activism.

Chief Roberto Villaseñor said at the time that Reyes was not targeted based on his race, as the officer who cited him was also Hispanic.

Reyes did not have a driver’s license, and a backup officer found that he had never had one, which is a misdemeanor offense under Arizona law that required police to impound the vehicle, Villaseñor said.

Other factors the officer took into account in evaluating whether to call the Border Patrol were Reyes’ limited English proficiency and that his passenger, Robles, also had no license or ID and no English proficiency, and neither would provide further information to police, department spokeswoman Sgt. Maria Hawke said at the time.

“This is racial profiling, pure and simple,” Christine Sun, an attorney with the ACLU Immigrants’ Rights Project, said in today’s news release. “Mr. Reyes and Mr. Robles were detained for no other reason than for the police to look into their immigration status and call the Border Patrol. This type of harassment should not be tolerated.”

Border Patrol agents took both men into custody and released them on bond days later. Reyes received a citation for a broken license place light and for driving without a license, which he paid in full, the release said. Robles was not charged for any violation related to the incident.

"At that moment I felt so helpless," Reyes said in the release. "It's so difficult to be in that situation, because you assume the police are there to protect people. When this happened, I thought they would call the Border Patrol, and that's exactly what they did. Many people are afraid to call the police now because they believe they will be harassed as I was."

In 2012, the U.S. Supreme Court declined to block SB 1070’s so-called “show me your papers” provision from going into effect because it found a “basic uncertainty” about what the provision actually requires of law enforcement officers.

The ACLU has been monitoring local agencies’ implementation because of worries that the law unconstitutionally authorizes and encourages illegal police practices.