Localities should be left to be the laboratories of democracy. If localities want to have policies that are patently foolish, they should be free to do it. As local as possible is the best level to decide things like this. Decentralized power is the necessary firewall.
“Localities should be left to be the laboratories of democracy. If localities want to have policies that are patently foolish...Etc.”
Well, not a democracy, a Republic. Governed by laws not mobs or even local elected mobs.
Streets and sanitation and zoning are local responsibilities, and if a local community does something that harms a neighboring community like diverting a river or tearing up another community’s road that town or city can be held responsible, usually through a lawsuit to make whole with a claim for damages.
Immigration policy is a federal responsibility aimed at protecting all communities. Cities should not get to decide locally who has a right to remain in the United States. Experience damage as a result of a sanctuary city ignoring federal law? The locality in which an illegal commits a crime should start charging the releasing sanctuary city politicians as criminal accessories. It might not result in any convictions but it might make the point.
A very important concept, but one that deserves context. Under the current lamentable status if given the question of more government vs. less government, or the often similar choice of more centralized government vs. less centralized government, in most random circumstances the choices or less and/or less centralized government would be the proper direction for change. But not all questions are random. Circumstances meriting different answers exist.
On the spectrum from pure anarchy to absolute tyranny the Founding Fathers, most Freepers and still many Americans (although probably not as many as we'd prefer) choose to be closer to the anarchy end of that spectrum than where most people have lived throughout history. But they didn't choose anarchy. That doesn't work for any society much larger than Robinson Crusoe's. Moreover, the Founding Fathers provided us with an important, but often forgotten experiment on the limits of limited, decentralized, government: The Articles of Confederation. That was failing in spite of the best efforts of our great founding generation. In its place the Framers gave us a federal republic as a system under which the people were sovereign. With a small (but more than under the Articles) government whose powers were carefully and appropriately distributed across multiple, potential competing, levels and branches. Yes, they wanted to allow for local innovation and for new, good ideas to spread but some functions deserved to be in certain places and anarchic, unlimited experimentation wasn't intended.
Our freedom's decline lies not just in increased government and increased centralization thereof, but in shifting governmental functions outside the original scheme. Shifts to too high or too low levels are both problematic. Management of major crime was to be mostly a state level function. Federal law has certainly usurped too much of that. The state might divide that power throughout multiple jurisdictions, but if one of those jurisdictions was having trouble maintaining law and order the state could supplement or even supersede it. Local officials attempting to block appropriate state powers, outside their intended domain, were deemed corrupt and were subject to the full range of state intervention. Successful innovators on subjects within their local domain could be promoted to higher levels by the local electorate to dabble in higher level matters as their representative. But on measures belonging at the state level localities got no more than the share of their representative vote's control. They couldn't unilaterally declare themselves beyond the reach of the state tax code, state murder statues, etc.
The Framers placed control over who could enter the country as a whole, and citizenship therein, at the Federal level. This makes sense. Free choice of citizens on in which state they'd lived and free trade within the various states was important and encouraged innovation. If Tennessee's government policies didn't work as well as Kentucky's folks could vote with their feet costing Tennessee population, tax base and power. But if Tennessee (initially a border state) would let any old "riff raff" in as Tennessee citizens, then the above implied Georgia would have to accept any of those "riff raff" who chose to move from outside the country, through Tennessee, to Georgia. Instead Tennessee could plead its case at the Federal legislature that such weren't really "riff raff" but worthy proto-Americans, but would have to convince enough other states before they could win admittance to the country as a whole. Want to shift functions to different places than the original scheme? There are mechanisms to change the scheme, with the consent of all concerned (or at least a supermajority thereof) through amendments to the formal "schemes," aka Constitutions, of the Federal and various state levels. But, by itself, Dodge City doesn't get to set all the policy for Kansas as a whole, nor for St. Louis, all of Missouri nor for the country as a whole.
These liberal/'progressive' sanctuary cities/states are blocking laws and making decisions that constitutionally belong at higher level of governments. They are corrupt choices amounting to insurrection. The Constitution, as legally amended, contains a remedy in Amendment 14, Section III. In contrast, conservative sanctuary cities, etc. against gun grabbers are defending the supreme law of the 2nd amendment against unconstitutional usurpers in the intermediate levels of government. They are not the same thing in spite of the progressive's exhortations.