Interesting column by Charles Krauthammer:
Regardless of your feelings on the substance of the immigration issue, this is not how a constitutional democracy should operate. Administrators administer the law, they don’t change it. That’s the legislators’ job.
[…]
This contagion of executive willfulness is not confined to the federal government or to Democrats. In Virginia, the Republican attorney general has just issued a ruling allowing police to ask about one’s immigration status when stopped for some other reason (e.g., a traffic violation). Heretofore, police could inquire only upon arrest and imprisonment.
Whatever your views about the result, the process is suspect. If police latitude regarding the interrogation of possible illegal immigrants is to be expanded, that’s an issue for the legislature, not the executive.
VIVIAN J. PAIGE | All Politics is Local 
Good perspective. I think lots of the issues in this country could be solved if the laws already on the books were enforced.
That applies to immigration, gun control, and others
“If police latitude regarding the interrogation of possible illegal immigrants is to be expanded, that’s an issue for the legislature, not the executive.”
Only if the restriction that “police could inquire only upon arrest and imprisonment” was a restriction passed by the legislature in the first place. That may be the case, but that has not been demonstrated to be the case. I have read the federal immigration law, and found no such restriction. A search on “immigrant” in the VA State Code also reveals no such limitation of police powers.