Charles Evans Hughes, Henrietta Mills v. Rutherford County…
“ It must appear that the enforcement of the tax would cause irreparable injury, or that there are other special circumstances bringing the case under some recognized head of equity jurisdiction, before the aid of a federal court of equity can be invoked. The mere fact that the validity of the tax may be tested more conveniently by a bill in equity than by an action at law does not justify resort to the former. ”
