The general rule is always stated to be that an injunction will not be granted to stay criminal or quasi-crininal proceedings. The original basis of the rule, it is quite generally agreed, was founded upon the theory that to sustain a bill in equity to restrain or relieve against proceedings for the punishment of offenses would constitute an invasion of the law courts. This theory was the natural outgrowth of the lack of relation between equity and law courts as they formerly existed in England. With the gradual ebb in the jealousies and antagonisms between courts of law and of equity, culminating in the joining of the two, much of the force of this theory disappeared. Without in any way abandoning the general rule, however, courts began to find and apply other reasons for asserting it. By far the most important reason modernly assigned for the denial of injunctive relief against criminal prosecutions, is that there is an adequate remedy at law. By this it is meant that the opportunity of the party accused to establish his innocence, or the invalidity of the law, by motion to dismiss, habeas corpus, plea, or by taking an appeal if convicted, is an adequate remedy.
Frederick G. Hamley,
Notes and Comments,
Injunctions to Restrain Threatened or Impending Criminal Prosecutions,
Wash. L. & Rev.
Available at: https://digitalcommons.law.uw.edu/wlr/vol6/iss3/4