Commonwealth regulation is based on the interstate and international trade and commerce power.

States laws related to commerce powers can be valid so long as Congress is silent on the matter.

This resolved a historic controversy over federal interstate commerce powers.

For the first time in half a century the majority has second-guessed Congress's exercise of its commerce power.

"I don't think there's a scholar out there who believes that the commerce power is without check," he told me confidently.

For example, the Court has allowed Congress to expand its regulatory power over all aspects of the nation's economy through the commerce power.

That is because the opinion relied on abstract categories to decide whether something is within or outside the commerce power.

Now that the commerce power is understood to extend across the economy, he said, only a complete exclusion for employment would accomplish the goal of Congress.

The decision said Congress may regulate state activities under its commerce power only as part of a "generally applicable" regulation of the private sector.

By passing legislation, Congress indicates its conclusion, whether explicitly or not, that facts support its exercise of the commerce power.