American Border Patrol observes, records, and reports. They are a "neighborhood watch" for the border area. They don't intercept, detain, or otherwise interfere with the border invaders or the Border Patrol.
If they're "vigilantes" then so is every neighborhood watch group in America.
"GLENN SPENCER TO REUTERS: The day you fire Deborah Tedford is the day I grant another interview to Reuters."
Border Hawk Now a Vigilante* Reuters Says ABP Takes Law Into Its Own Hands