The main purpose of this legislation is to prevent states from imposing taxes on nonresident individuals for assets they owned before the law was enacted. The goal is to protect individuals who do not live in a state from being taxed retroactively on their assets, which could create financial burdens and discourage people from investing or owning property in that state. The key provision of this law is a clear prohibition against states taxing nonresidents based on the value of their assets if that tax is based on any time before the law takes effect.