How do bills of attainder and ex post facto laws reflect the principle of separation of power

The United States Constitution prohibits legislative bills of attainder. Which is indicated in federal law under Article I, Section 9, and in state law under Article I, Section 10.  Being banned under state law reflects the significance that the framers are connected to this issue.

The clauses that are prohibiting attainder laws serve two purposes within the U.S. Constitution. They strengthened the separation of powers by means of prohibiting the legislature to execute judicial or executive functions, because  the result of any such acts of legislature would take the form of a bill of attainder. Additionally, they incorporate the conceptualization of due process, that was relatively reinforced by the Fifth Amendment to the Constitution. The text of the Constitution, Article I, Section 9, Clause 3 states that "No Bill of Attainder or ex post facto Law shall be passed". Moreover, the constitution of every state clearly progibits bills of attainder as well. For instance, the Wisconsin's constitution under Article I, Section 12 states that, “No bill of attainder, ex post facto law, nor any law impairing the obligation of contracts, shall ever be passed, and no conviction shall work corruption of blood or forfeiture of estate.” On the contrary, the Texas version under Article 1 (Titled Bill of Rights) Section 16, entitled Bills of Attainder; Ex Post Facto or Retroactive Laws, Impairing Obligation of Contracts states that, "No bill of attainder, ex post facto law, retroactive law, or any law impairing the obligation of contracts, shall be made".  It is not clear though whether a contract that calls for heirs to be denied of their estate is permitted under this law.

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