[Ultra Sonic 007]

I believe you’re referring to Posse Comitatus?

Because if so, that’s a federal act...but it’s not in the Constitution.

http://en.wikipedia.org/wiki/Posse_Comitatus_Act

This act explicitly prohibits the military or any other such unit (like the National Guard) under federal control from acting in a law enforcement capacity within the United States.

Now the question becomes: is halting the drug cartels streaming past our open border a matter of law enforcement, or is it more of a military matter?

[Obamageddon]

Posse Comitatus only applies to Army forces. The Naval forces are not and never were subject to it.
Specifically, the Marine Corps is not subject to Posse Comitatus

[Born In America]

This act explicitly prohibits the military or any other such unit (like the National Guard) under federal control from acting in a law enforcement capacity within the United States.

That is correct in terms of the United States Military as defined by the respective branches. However, the President can call forth the Militia(National Guard)and the President cannot organize, arm or discipline the Militia. All of those powers belong to Congress....

Article 1, Section 8

[Las Vegas Ron]

a matter of law enforcement, or is it more of a military matter?

I believe it could be considered an invasion which would justify military action

[occamrzr06]

This act explicitly prohibits the military or any other such unit (like the National Guard) under federal control from acting in a law enforcement capacity within the United States.

Here is a little history on that "Act"...

http://www.carlisle.army.mil/USAWC/parameters/04autumn/felicett.pdf

[DesertRhino]

I call it what it is, the Mexican have an open insurgent criminal rebellion on their hands. It is located directly on our border and is a clear threat to Americans on this side. Nothing in the constitution that i can see prevents our military forces being deployed in a defensive posture along the national border.

We deploy Naval and Air Forces for other threats at the border, and dont just assume every incursion is handled with a fine from the FAA or a visit from a customs agent.