Though state laws vary, many states have laws against making license plates unreadable. New York charges a fine for covers, according to the Times Union. California vehicle code section 5200-5206 also disallows covers, notes the Legislative Council of California.
Florida law also bans the use of anything that obscures any part of the license plate, explains Local10.com. States require that all license plates be clean and easy to read, notes LegalMatch. The plate must not be obstructed, and the numbers must be easy to read. In addition to the license plate being clean and clearly visible, 31 states have laws require that all vehicles have both a front and back license plate, as of 2013, according to Cars.com.