May 16, 2006 per President George W. Bush:
One way to help during this transition is to use the National Guard. So in coordination with governors, up to 6,000 guard members will be deployed to our southern border. . . . This initial commitment of guard members would last for a period of one year. After that, the number of guard forces will be reduced as new Border Patrol agents and new technologies come online. It is important for Americans to know that we have enough guard forces to win the war on terror, to respond to natural disasters, and to help secure our border.
December, 2005 per Secretary of Homeland Defense Chertoff:
Well, the National Guard is really, first of all, not trained for that mission. I mean, the fact of the matter is the border is a special place. There are special challenges that are faced there.... I think it would be a horribly over-expensive and very difficult way to manage this problem.
Hat Tip to Defense Tech.