I don't think it would be legal to go to the border and use humans on the other side for target practice. Furthermore I do not think that waiting for an illegal immigrant to cross over the border and then shoot them is a legal bloodsport. I would exercise caution before killing anyone until a ruling comes down on the issue. I think it is lawful for authorities that have been assigned the job of border security to act in the manner directed. I also believe that if you own property on the border you have a right to defend your property.
If the government is not securing our border to your satisfaction you need to vote harder!