Federal law or State law

In US, every State can make their own law, in some areas. This has advantages and disadvantages.

This model helps when we are trying to solve a problem which needs some kind of radical action. In such circumstances, adventurous State can take the first leap, recklessly, when every other States are contemplating. Such adventurous states set standard and cultivate the minds of dis-aggrieng people to accept the change. Example: Califorina seems to take a leap when it comes to environment laws, and this may convince other states to adapt atleast some of the changes.

Negative thing is, when we are trying to solve mundane problems. In these circumstances, we may end up solving same problem again and again for every State. Example:- When it comes to voting policies, every state has its own law, and a good voting system is needed, and this is something for which everyone is going to agree, so we can make a one blanket federal law to solve once for all states.

I should conclude saying that this is lay-man's view.