This is in fact unconstitutional.
I sencerely hope this law (if it passes) gets challenged in courts. It is unconstitutional on at least two counts:
1. You can not change the law retroactively (ex post facto)

"A large "exception" to the ex post facto prohibition can be found in administrative law, as federal agencies may apply their rules retroactively if Congress has authorized them to do so. Retroactive application is disfavored by the courts for a number of reasons,[4] but Congress may grant agencies this authority through express statutory provision. Furthermore, when an agency engages in adjudication, it may apply its own policy goals and interpretation of statutes retroactively, even if it has not formally promulgated a rule on a subject."