Who the heck carries around five pairs of handcuffs? Were these guys off-duty police? If not, and they're patrolling the desert looking for illegal crossers, I'm all for it but, hey! Find out whether or not it's legal first! Sheesh.
Following your logic, the next time I see a crime being committed...a mugging or perhaps a rape...I'll just keep walking and ignore it since I'm not sure "...whether or not it is legal for me to interfere".