Rufus Wheeler Peckham, Indiana Manufacturing Company v…
“ It has long been the settled doctrine of the Federal courts that the mere illegality of a tax, or the mere fact that a law upon which the tax is founded is unconstitutional, does not entitle a party to relief by injunction against proceedings under the law, but it must appear that the party has no adequate remedy by the ordinary processes of the law, or that the case falls under some other recognized head of equity jurisdiction, such as multiplicity of suits, irreparable injury, etc. ”
