I mean in the end, the high ranking LAPD officers told Miles that he was out of their juristiction because he was on the other side of the border. But wasn't the LAPD already out of their juristiction of the City of LA?
shareYes, but it probably still would have been legal to detain him as long as he was within the U.S.
It's all moot anyway after 9/11. I'm pretty sure the Border Patrol on either side would not have let him just waltz across to Mexico and have a Kodak moment with the LAPD. He would have been shot dead by a sniper. Just enjoy the movie for what it is and try not to question it too much.