You are wrong as usual. If the federal government had sent in the National Guard then they could only be observers but that is not what happened, Perry sent them without Feds so he can grant them police powers.
http://www.nytimes.com/2014/07/25/us/national-guard-in-texas-could-get-arrest-power.html?_r=0
not true.
Their official orders are to be OBSERVERS only. NO arrest powers will be given. The head of the border patrol has said so publicly, indicating the National Guard has no training to deal with immigrants.
The National Guards only function will be to observe and report.
TOS.