Sanctuary cities

These are cities where, for some reason, the flouting of immigration laws is accepted.....by the people, by the lawmakers, by the police, by the state governments in which they exist, and by the Federal Government...

Why?

Why is the flouting of any law acceptable? It isn't that the law is illegal....It isn't that the laws are not enforced elsewhere in that state or in the country.....just in certain cities where the Mayor or whatever they call the leader of that municipality has "Decreed" that these Federal and State laws will not be enforced........

In other words, the Mayor of San Francisco has declared that we can ignore certain laws...

And the higher governments accept it, and acquiesce....They, by failing to enforce the laws, agree that it is acceptable to break them.

What if a municipality (or a state) were to decide that other Federal laws were acceptable to ignore?

Say gun laws, or marriage laws. O laws regarding finance?

Or, say, tax laws?

What would happen then? If it came about that the city of, say, Ottumwa, Iowa decided that all laws regarding the manufacture (or transfer) of firearms were null and void, would the Federal government look the other way? How about the State?
How about if Reno, Nevada decided that there need be no licences to handle nuclear materials? How about if Ogden,Utah decided that there need be no currency or banking laws, and allowed anyone to deposit any amount of money in a bank, with no records as to where it came from? What if the town of Athens,Georgia outlawed homosexuality...Made it an offense punishable by a year in jail?

Would the Feds just shrug and look the other way?

While I do feel that there are too many laws, and many are unconstitutional, these are laws. Either enforce them, or take 'em off the books.

Why does the Federal Government fail to enforce their own laws in "Progressive" cities? Why is that acceptable?