No contract-based Takings claim, as there was no contract.
Legislative enactment does not create a property interest cognizable under the Takings Clause.
Dissent: Contract.
http://www.cafc.uscourts.gov/sites/default/files/opinions-orders/17-1224.Opinion.6-14-2018.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.