Most states will allow you to pull things including a Wakeboard behind the Jet Ski as long as you have a spotter but some states may not allow you to pull the Wakeboard or anything with a Jet Ski with or without a spotter.
And to pull a Wakeboard or anything else behind a Jet Ski you need to have mirrors but the laws can vary depending on locality so it's best to get the information on local laws to be sure.
If you're caught you might just get a warning about it but then again you might get a fine as it depends on the officer who spots you.