Can criminal law be retroactive

In administrative law, federal agencies may apply their rules retroactively if Congress has authorized them to; otherwise, retroactive application is generally prohibited.
Retroactive application of regulations is disfavored by the courts for several reasons.
What does it mean when a law is not retroactive? .

The truth about the minister’s housing allowance is that it is NOT retroactive; it is only projective.
What exactly does this mean.
The housing allowance (or exclusion) is applicable from the date it is approved through the end of the year.

The first is that this law, if passed, will be retroactive:

Retroactive child support is not the same as arrears.
Retroactive support refers to child support that accrued before a judge issued a child support order.
Arrears only occur after the court finalizes the child support order.
In many states, when a parent files for divorce or a standalone child support case, the court will backdate the support ..