Troops should not be used in law enforment situtations period..
Let's say Al-Queda have taken control of several small towns and have sealed them off. The police forces can't handle the increasing numbers of terrorists. They are beheading Americans within those towns...are you saying no military action should be taken to free those Americans?
You're entitled to your opinion. But American history and the law are against you.
The Posse Comitatus Act is widely misunderstood by both the left and right. The author is basically wrong to write "prohibit[s] the use of the military in enforcing laws." It's semi-common for military forces to enforce laws or help enforce laws.
(For one thing, the Act only applies to the U.S. Army, not to National Guard or other troops working under state command. And even with regard to the U.S. Army there are exceptions in the law.)
I would see troops on the border as guarding our border which I would assume is one of their potential duties. Protecting the border would not seem to fall under enforcing the law to me. If they catch someone crossing then they turn them over to the law enforcement agency charged with such activities. No different than a civilan catching an illegal and turning him over to the Border Patrol. Now if you have soldiers running around arresting people for civilian crimes then there might be a problem with that. Also, if the military cannot enforce laws while located inside the country then how do they prevent people from stealing stuff from their bases here?