It depends on the law in your jurisdiction and, potentially, on promises you may have made in your employment agreement. Many jurisdictions will allow employers to enforce an IP agreement which you made as a condition of your employment, and employers in both these and under jurisdictions at least theoretically state claims to such IP in a lot of employment agreements or in appendixes to them. (e.g. buried in the Com…
Absolutely agree. I used to work in Vegas. An engineer colleague of mine specifically took a job there because (at that time?) Nevada was the only state, or one of very few, where an employer could not lay claim to his side projects - and he had at least one patent that I know of.
If you are in a place where the employer can lay claim to your side work, then that means you need them to agree to not do so in your contract. There is a demand for software engineers now, so they should sign it.