Louis Brandeis

“ As local rates may be so low, and the circumstances such, that these rates must be raised in order to protect interstate commerce, so a tax on the privilege of engaging in local business may conceivably be so high, and the circumstances such, as to require lowering of the tax in order to protect interstate commerce. But the high tax on the local privilege, like the low rate for the local traffic, if it burdens interstate commerce at all, does so by reason of its consequences. ”

“ Such control over intrastate commerce exists because it is a necessary incident of freeing interstate commerce from burdens, obstructions, or discrimination. It has been exerted wherever Congress deemed that the state's power to regulate and promote intrastate commerce is exercised in such a way as to prejudice the interstate. ”

“ The interstate business is found profitable when carried on in connection with the local, because the expenses of the joint operation are, under applicable accounting rules, apportioned between the two branches of the business. ”