The Constitution of the United States mentions three areas of jurisdiction in which the courts may operate:

Common Law

Common Law is based on God's Law. Anytime someone is charged under the Common Law, there must be a "damaged party". You are free under the Common Law to do anything you please, as long as you do not infringe on the life, liberty or property of someone else. You have a right to make a "fool" of yourself provided you do not infringe on the life, liberty or property of someone else. The Common Law does not allow for any government action which prevents a man from making a fool of himself. For instance, when you cross over state lines in most states, you will see a sign which says, "BUCKLE YOUR SEAT BELTS - IT'S THE LAW." This cannot be Common Law, because who would you injure if you did not buckle up? Nobody. This would be compelled performance. But Common Law cannot compel performance. Any violation of Common Law is a CRIMINAL ACT, and is punishable.

Equity Law

Equity Law is law which "compels performance". It compels you to perform to the exact letter of any contract that you are under. So, if you have compelled performance, there must be a contract somewhere, and you are being compelled to perform under the obligation of the contract. Now this can only be a civil action, not criminal. In Equity Jurisdiction, you cannot be tried criminally, but you can be compelled to perform to the letter of the contract. If you then refuse to perform as directed by the court, you can be charged with a criminal action. Are our seat belts Equity laws? No. They are not, because you cannot be penalized or punished for not keeping to the letter of the contract.

Admiralty/Maritime Law

This is "civil" jurisdiction of Compelled Performance which also has Criminal Penalties for not adhering to the letter of the contract, but this only applies to International Contracts. Now we can see what jurisdiction the seat belt laws (and all traffic laws, building codes, ordinances, tax codes, etc.) are under. Whenever there is a penalty for failure to perform (such as willful failure to file) that is Admiralty/Maritime Law and there must be a valid international contract in force. However, the courts don't want to admit that they are operating under Admiralty/Maritime [hereafter noted by A/M] Jurisdiction, so they took the international law or Law Merchant and adopted it into our codes. This is what the SC decided in the Erie vs. Tomkins - that the decisions will be based on commercial law or business law and that it will have criminal penalties associated with it. Since they were instructed not to call it A/M Jurisdiction, they call it Statutory Jurisdiction.