The armed men, including one with an AR-15 semi-automatic assault rifle slung over his shoulder (similar to the model pictured above), demonstrated with protesters outside a convention center where the president was giving a speech, according to AP reports.
The gun-toters didn't need permits, according to the Phoenix police. No crimes were committed, and no one was arrested.
This is not the first time armed protestors have appeared at an Obama event.
Last week, a man in New Hampshire stood outside with a pistol strapped to his leg and carried a sign reading "It is time to water the tree of liberty". The sign was paraphrasing Thomas Jefferson's oft-quoted missive to William Stephen Smith in 1787, i.e., "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants."
The man with the assault rifle declined to be identified, according to the AP, but told The Arizona Republic that he was carrying the assault weapon because he could. "In Arizona, I still have some freedoms," he said.
Police who were monitoring the man at the downtown protest said they also wanted to make sure no one harmed him.
"Just by his presence and people seeing the rifle and people knowing the president was in town, it sparked a lot of emotions," Oliver said. "We were keeping peace on both ends."
Arizona is an "open-carry" state, meaning anyone who is legally allowed to have a firearm can carry it in public as long as it's visible. A permit is required if the weapon is carried concealed.