Why Change the Guard-The Border
I do not want to close the border at this very moment, but I want to know that we can when we have to. I believe at this time we could not do that in the case of an epidemic or true emergency. The group that would best be positioned to handle this would be the Homeland Security and the National Guard. By placing the Army and Air National Guard in Homeland Security it could focus on budgeting for the event we need to close or regulate the border with Mexico.
The same practices that are used to find narcotics in the southwest would apply, not using local units but formations from other areas of the country. This prevents illegal markets from forming and the locals would not be able to infiltrate the intelligence gathering efforts of the Guardsmen. During my time on federal duty at Twentynine Palms the Army was used for counter narcotics operations around 29 and the Marines were sent to Texas for the above explained reasons.
This would not really affect the ability of the Army and Air Guard to be the primary back up formations for the federal parent organizations, it would actually add very needed skills and training.