While the definition may vary from country to country, in the US it's pretty black and white.
http://en.wikipedia.org/wiki/Copyright

Quote - In the United States, copyright has been made automatic (in the style of the Berne Convention) since March 1, 1989, which has had the effect of making it appear to be more like a property right. Thus, as with some forms of personal property, a copyright need not be granted or obtained through official registration with any government office. Once an idea has been reduced to tangible form, for example by securing it in a fixed medium (such as a drawing, sheet music, photograph, a videotape or a letter), the copyright holder is entitled to enforce his or her exclusive rights. However, while a copyright need not be officially registered for the copyright owner to begin exercising his exclusive rights, registration of works (where the laws of that jurisdiction provide for registration) does have benefits; it serves as prima facie evidence of a valid copyright and enables the copyright holder to seek statutory damages and attorney's fees (whereas in the USA, for instance, registering after an infringement only enables one to receive actual damages and lost profits). The original holder of the copyright may be the employer of the actual author rather than the author himself if the work is a "work for hire". Again, this principle is widespread; in English law the Copyright Designs and Patents Act 1988 provides that where a work in which copyright subsists is made by an employee in the course of that employment, the copyright is automatically owned by the employer which would be a "Work for Hire."

People can consider it a stinky, dumb, mean, farty old inconvenient body of law, but it's still law.

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