Here's why:
Heidi Cruz's work for the Council on Foreign Relations: Building a North American Community
...The Task Force’s central recommendation is the creation by 2010 of a North American community to enhance security, prosperity, and opportunity. Its boundaries will be defined by a common external tariff and an outer security perimeter within which the movement of people, products, and capital will be legal, orderly, and safe. Its goal will be to guarantee a free, secure, just, and prosperous North America...