Well let's see here. If it is a constitutional problem to enforce a federal law on immigration violations then should the local LEO's enforce armed robbery of Federal Banks? Of violations of federal firearm laws? Of using fraudulent passports and other federally issued documents? Of federal possession of federally prohibited explosives or other harmful detonating devices? The list could go on and on if one starts thinking about the many federal laws that the locals already enforce or make arrests for during the course of a routine day. I think you get my point here.
I'm not trying to be flippant but the analogy you proffered isn't unique but one the OBL types like to present as reasons why not to enforce our federal immigration laws and stopping the mass invasion of the law breakers from outside our borders.
