Earlier quoted context omitted.
These grandfather clauses irk me... if the policy is not good enough to stand on its own then it should not be policy.
Ex post facto laws are anathema.
Yes, the only reason the government is hiding time machines from us is their inability to finish the tax laws that would apply :)
Analogy: If congress raises gas taxes (nobody said analogies have to be realistic), everyone would have to pay more at the pump. But that doesn't mean the tax is applied retroactively.