 It is argued that the wall simply forces illegal border crossings to be moved to the more dangerous area of the Arizona desert.In 2006, the U.S. Congress passed the Secure Fence Act of 2006
which authorized spending $1.2 billion to build 700 miles (1,100 km) of additional fencing on the southern border facing Mexico.Tunnels under the wall are still a common way to illegally cross the border.