Police officers in a community abutting the Mexican border just got new authority to pursue lawbreakers and assist in rescues beyond city limits.

Weighed down with four liters of water, Mexican Alfredo Cázares embarked on a risky, illegal journey across the U.S. border and into the sweltering Arizona desert beyond.

Deep in the Arizona desert on the southern U.S. border, a surveillance tower rises more than 150 feet (46 m) into the air, ...