Article I Section 17 Pennsylvania Constitution
Article I Section 17 Constitution of the Commonwealth of Pennsylvania is about Ex Post Facto Laws; Impairment of Contracts. Article I is titled Declaration of Rights, it has a preamble and 29 sections.
Ex Post Facto Laws; Impairment of Contracts
No ex post facto law, nor any law impairing the obligation of contracts, or making irrevocable any grant of special privileges or immunities, shall be passed.
See also: Article I Section 16 Pennsylvania Constitution