For a law to be passed there must be some reason for it otherwise lawmakers are just making laws for fun which isn't a responsible use of their position.
If we want our laws to make sense and stand upon science, evidence, and facts then these reasons should have to actually hold up when examined.
If we had this way of doing things then marijuana laws would've been invalidated a long time ago, since defendants could've brought in scientific experts to rebut the "reasons" for making it illegal.
The burden of proof should be on the defendant to show why the law fails to live up to its reasons and the government allowed to either rescind the law when it's invalidated or to appeal even up to the Supreme Court in order to weigh evidence. Though I think it would be even better to have a special Court of Science and Reason to weigh evidence for whether the law lives up to its reasons while the Supreme Court handles other constitutional issues.
In the current US system it is easier to make new law than remove old law, and few legislators review the books for laws that are outdated and should be removed. If the reasons for a law are proven false, the law needs to be removed or at least changed, and leaving it allows for it to be used as a weapon against people.