We've seen this movie, right?

With Alan Arkin, as Rico dimly recalls. But, no, this is for real:
"Mexican troops crossed the border into Arizona and held a US Border Patrol agent at gunpoint. Agents assigned to the Border Patrol at Ajo, Arizona said the Mexican soldiers crossed the border into an isolated area southwest of Tucson and pointed rifles at the agent, who has not been identified. The Mexicans withdrew after other American agents arrived on the scene, the Washington Times reports."
“Unfortunately, this sort of behavior by Mexican military personnel has been going on for years,” union Local 2544 of the National Border Patrol Council said on its website. “They are never held accountable, and the United States government will undoubtedly brush this off as another case of, ‘Oh well, they didn’t know they were in the United States'. It is fortunate that this incident didn’t end in a very ugly gunfight.”

Rico says this is going to turn ugly one of these days, and the Mexicans are liable to find themselves outgunned...