Ex Post Facto (which translates to "after the fact") does not apply. It would prevent writing tickets to people that had window tint prior to the law being written, but have complied since the law was passed.
For example, if the drinking age was raised from 21 to 25 today, officers could not ticket a 21 year old they saw drinking yesterday. They could, however, ticket him if they saw him drinking tomorrow.
17years law enforcement