Second, Congress is empowered to regulate and protect the instrumentalities of interstate commerce, or persons or things in interstate commerce, even though the threat may come only from intrastate activities.

A familiar like exercise of power is the regulation of intrastate transactions which are so commingled with or related to interstate commerce that all must be regulated if the interstate commerce is to be effectively controlled.

We have held that, in dealing with common carriers engaged in both interstate and intrastate commerce, the dominant authority of Congress necessarily embraces the right to control their intrastate operations in all matters having such a close and substantial relation to interstate traffic that the control is essential or appropriate to secure the freedom of that traffic from …

And, as Congress has power, when necessary for the protection of interstate commerce, to regulate intrastate transactions

"[T] he Necessary and Proper Clause does not give `Congress... the authority to regulate the internal commerce of a State, as such,'but it does allow Congress `to take all measures necessary or appropriate to'the effective regulation of the interstate market, `although intrastate transactions... may thereby be controlled.'"

—the Court held that railroad rates of an admittedly intrastate character and fixed by authority of the state might, nevertheless, be revised by the Federal Government because of the economic effects which they had upon interstate commerce.

Defendants apparently concede that, consistent with the Commerce Clause, Article 1, § 8, US Const., Congress could have authorized the Commission to regulate rates charged by motor carriers between points within a state where such transportation was in the stream of commerce and the rates were found to have a substantial effect on interstate commerce.

—sustaining the authority of the Interstate Commerce Commission to prescribe intrastate railroad rates that substantially affect interstate railroad traffic

Although the Court upheld a fair amount of the ensuing legislation as being within the commerce power,

—a power to prevent unjust preference to particular intrastate shippers or localities at the demonstrated expense of interstate commerce.