> but not readable by a machine has the law been violated

IANAL but I think that would be a violation, since it falls under the "detectability" of a "feature" being "recorded".

> A person may not apply or attach [...] onto or around [...] which interferes with the legibility, angular visibility, or detectability of any feature or detail on the license plate or interferes with the ability to record any feature or detail on the license plate. A person who knowingly violates this section commits a misdemeanor of the second degree.

https://www.flsenate.gov/Session/Bill/2025/253/?Tab=BillText