No. 'Ex Post Facto' laws are specifically prohibited by the US Constitution. Explanation:
Ex post facto
Latin for "from a thing done afterward." Ex post facto is most typically used to refer to a law that applies retroactively, thereby criminalizing conduct that was legal when originally performed. Two clauses in the US Constitution prohibit ex post facto laws: Art 1, § 9 and Art. 1 § 10. see, e.g. Collins v. Youngblood 497 US 37 (1990) and California Dep't of Corrections v. Morales 514 US 499 (1995).
http://www.law.cornell.edu/lexicon/ex_post_facto.htm
Ex post facto laws are specifically prohibited by the Constitution.
Retroactive criminal laws that criminalize an action that was not illegal when committed. Laws that increase the punishment for a crime after it has been committed. Laws that change the rules of evidence required for conviction after the crime has been committed. Laws that alter the legal consequences of an action that was lawful when performed.
passing ex post facto laws
No. Article I, Section 9, paragraph 3 of the Constitution prohibits Congress from passing ex post facto laws.
The U.S. Constitution forbids any law that conflicts with existing Federal laws. It also forbids any law that violates the Constitution itself.
passing ex post facto laws
(in the US) Ex Post Facto laws are forbidden by the US Constitution.
Prohibited by Article 1 Section 9 of the U.S. Constitution
The U.S. Constitution prohibits both the federal and state governments from passing ex post facto laws. This means that laws cannot be applied retroactively to criminalize an action that was legal when it was committed. Such laws are considered unfair and a violation of due process.
Assuming this is about the united states, to pass an ex post facto law is no kind of power, it is prohibited by the constitution.
"Ex post facto", or "after the fact" laws, and Bills of Attainder, which specifically seize the property of named persons.
In the US - there is no such thing. They are known as "Ex Post Facto" laws and are forbidden by the Constitution.