[lukevdp]

Depends entirely on the employment agreement. Many will automatically assign ownership of any code written to the employer.

[Sanzig]

Which, depending on case law in a particular jurisdiction, may or may not actually be enforceable. This is exactly why you would want to talk to a lawyer: they can tell you if you have a leg to stand on.

The employer might be under the impression that all the terms in the employment contract they pulled off FreeLegalTemplates.net are enforceable when they aren't. Going to a lawyer first gives you the ammunition to politely point out that you are in fact the one in the right here.

[Aeolun]

Which is insane, and should be illegal in a variety of different ways.

[prox]

Well true, depends on circumstances and how OP and employer relate and if they can find a win-win for both. See it as an opportunity.