Curtis concluded that the federal government enjoyed exclusive power to regulate commerce only when the thing regulated required national uniformity.

Some argue that centralisation and national uniformity were fine for the era of mass production, but that the service-based economy of the future demands diversity.

The Court had held in Cooley v. Board of Wardens (1852) that legislation which required national uniformity was reserved exclusively to Congress.

Congress could decide at any time that national uniformity was preferable and could pre-empt the state and local laws, he said.

He believes the definition is too broad and "offer little guidance to judges and will bring about no national uniformity in sneak and peek cases."

Proponents believe that both greater certainty and national uniformity are necessary for meaningful protection in today s marketplace, especially in the on-line world.

Business members of the association said they wanted absolute national uniformity on what is taxed.

These guidelines should ensure a degree of national uniformity.

A national uniformity in the results of similar cases was sought.

But "if Congress had intended to disrupt national uniformity in all of these matters" it would have done so directly, rather than obliquely, he said.