Can you flesh that out a bit? What is the law? Who has to abide by it?
In Russia there are Federal Migration Service and you have to inform it every time you are moving somewhere for any prolonged period of time. Technically, you may have issues with authorities if they fond you registered in one district and living in another but it is estimates about 30% of population are simply ignoring the rules as their official and factual residences aren’t match.
Most of the European countries has similar rules and unlike Russia they are enforcing it with fines and imprisonment.
It is even worse in China. Not only you have to inform the government if you are moving, in some cases you need permit from authorities.