If by "illegal" you mean is the employer facing criminal charges for theft or unlawful taking - no.
As an employer, (unless there is some employer/employee contract stating otherwise) they automatically own all work product that you produce while acting within the scope of your employment; whether that's a full article or story submitted for publication, or handwritten notes on a cocktail napkin. If it was written for an employer by an employee, the company owns it and enjoys all rights related to it - and they don't need a written contract or other document that says so (per the Copyright Act). As such, they have no legal obligation to credit a specific author, although they may be in troubled legal waters if they credit it to a specific person fraudulantly.
Here's some good info from the Florida Bar Entertainment, Arts, and Sports Law Section:
http://www.easl.info/modules.php?op=...article&sid=27
As always, you should get an opinion from a licensed Florida attorney who deals specifically with these types of cases (you're looking for someone who practices under copyright law, or sometimes it's called "intellectual property law").
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