PHOENIX -- A member of the Maricopa County sheriff's posse made up a law to prevent someone from videotaping a traffic stop, video footage shows.

During the Maricopa County Sheriff's Office Jan. 9 crime-suppression sweep, Sal Reza and a group of observers took video cameras to film the arrests.

"We're part of a coalition of people that … have been monitoring the Arpaio sweeps for racial profiling," Reza said. "We hope to document any abuse that may happen."

On Jan. 9, two deputies in Goodyear pulled a car over, saying the woman was driving without her headlights. As the deputies questioned her outside, her young children were crying, and as Reza videotaped the incident, a posse member approached him.

The footage recorded the posse member saying, "Those deputies are undercover so you can't shoot here … I told you, you can't videotape -- it's against the law."

"The sheriff's posse member had absolutely no right to do that," said Dan Barr, a First Amendment Attorney.

According to Barr, there is no law that prohibits people from videotaping police scenes, even when undercover officers are involved. In fact, people have the right to observe and document anything that takes place in public view.

"It's disturbing to see a member of the sheriff's posse walk up and simply make up a law that doesn't exist," Barr said.

Reza believes the sheriff's deputies and posse members did not want him videotaping an emotional scene.

"In reality to me, (the tape) shows that that's no way to enforce immigration law," Reza said.

Lt. Charles Siemens, who is in charge of the sheriff's posse program, said the posse member was only trying to protect a pair of undercover officers.

"It's not a matter of trying to restrict people's ability to film or document things," Siemens said.

Siemens said he was frustrated with the posse member quoting a law that didn't exist.

For his part, Reza said the sheriff's office has an interest in protecting its deputies; however, he believes his role documenting the sweeps is also important.

"I can see what they're trying to do, but at the same time I'm willing to assert my rights under the Constitution," he said.

And the woman who was pulled over? It turned out she was wanted for failing to pay a parking ticket, and she has been deported to Mexico.

Her children are U.S. citizens.