[danielf]

If this exercise was part of their military training (however trivial), they are on dodgy grounds. The British military can't just go and train in another nation without declaring it/asking permission. If this is just a case of people pursuing their hobbies it's another matter, but if the whole team were military who were not on leave, and the rescuers were as well it does look like military training on a tourist visa and the Mexicans have every right to complain.