The framers of the Constitution of the United States faced the dual challenge of .
providing a system strong enough to protect the citizens, while assuring that the citizens would not be oppressed. Ideas for the Constitution were borrowed from centuries of experience including the Magna Carta, English Parliament, John Locke, James Madison and from the experiences of the colonists themselves. I believe the strategies used have been quite effective since 1788 when the Constitution was adopted as the basic principals and rules of government for the United States of America. .
The policy of Federalism came about to bring all the states together under one central authority while still maintaining the freedom to make their own decisions and enact laws, as long as they don't overrule federal laws. This is the tenth amendment. It says "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people. For example, there is a federal tax on gasoline, but each state can charge an additional tax on top of that. Some states charge more than others. Each state is allowed to collect sales taxes for goods and services. The counties within each state can collect tax on top of the state tax if they require it. The federal government collects an income tax from each citizen every year. Each state also imposes an income tax on its residents. As a result some states are cheaper to live in than others. As far as laws go, any federal law has superiority over the states. This means that a state cannot make something legal which the federal government has said is illegal. The state can create stricter laws, but not go against federal law. The Supreme Court has the final say in all disputes.
The separation of powers means that the government's power is divided between the executive, legislative and judicial branches.