Regarding the Florida Legislature's similar effortsThe Florida Legislation Violates the Principle of Separation of Powers
Even beyond these constitutional infirmities, there are other defects in the Florida law. For instance, Article I, Section 10 of the federal Constitution prohibits each state from enacting any "bill of attainder"--a legislative act that imposes punishment on one or more people without the benefit of a trial.
A bill of attainder is the ultimate violation of both due process and separation of powers. That is because it substitutes a political process for the adjudication of a particular controversy by a court committed to making its decision based on the law, as the court best understands it. The due process violation is the deprivation of the court hearing. The separation of powers violation is the legislature's usurpation of the judiciary's authority to resolve individual cases.
The Florida law directed at Schiavo is not, as a technical matter, a bill of attainder. The U.S. Supreme Court has interpreted that term to apply only to laws that are designed to punish particular individuals, and the Florida legislators no doubt believed that they were bestowing a benefit on Schiavo by permitting the Governor to extend her life.
Yet certainly the spirit of the Bill of Attainder Clause is violated when a legislature and governor assume for themselves a judicial function--acting to override a judicial decision in a particular case.
Indeed, that was the holding of the United States Supreme Court in the 1995 case of Plaut v. Spendthrift Farm, Inc. There, in an opinion by Justice Scalia, the Court invalidated an effort by Congress to direct the courts to reopen final judgments.
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