Retroactivity of Legislation
RETROACTIVITY OF LEGISLATION
A characteristic of arbitrary government is that the state can alter retroactively the legal status of acts already done. Therefore, proposals to prohibit various types of retroactive legislation encountered the opposition of those delegates to the constitutional convention of 1787 who believed such laws were "void of themselves" and that a formal prohibition would "proclaim that we are ignorant of the first principles of legislation." There are, nevertheless, three such prohibitions in the Constitution: Congress may not pass ex post facto laws and the states may not pass ex post facto laws or laws impairing the obligation of contracts.
There are sound historical reasons for supposing that the Framers meant to proscribe both criminal and civil legislation with retrospective application. But john dickinson had warned the convention that william blackstone's commentaries treated "ex post facto" as a technical term applying only to criminal law. In calder v. bull (1798), the Supreme Court relied on Blackstone's authority to confine the constitutional prohibition to criminal laws.
The contract clause ultimately proved a mere parchment barrier to retroactive legislation. It does not apply to the federal government and the courts have so interpreted it as to make it a weak defense against retroactive state laws.
Dennis J. Mahoney
"Retroactivity of Legislation." Encyclopedia of the American Constitution. . Encyclopedia.com. (January 20, 2019). https://www.encyclopedia.com/politics/encyclopedias-almanacs-transcripts-and-maps/retroactivity-legislation
"Retroactivity of Legislation." Encyclopedia of the American Constitution. . Retrieved January 20, 2019 from Encyclopedia.com: https://www.encyclopedia.com/politics/encyclopedias-almanacs-transcripts-and-maps/retroactivity-legislation