Because outside Constitutionally enumerated areas, the federal government and the states have concurrent, not OVERLAPING jurisdictions.
And, because illegals are 'residents'....not *citizens* , they are protected by law.
Makes no sense - if an illegal immigrant robs a convenience store in a State, the local police can arrest and hold the guy - this is justan attempt to further blur the laws and make it easier for the ACLU commies to have their way.