In practice, this isn't likely to happen outside of California. Most companies are not going to sue you unless it's worth their while; that is, unless your side

In practice, this isn't likely to happen outside of California. Most companies are not going to sue you unless it's worth their while; that is, unless your side project is making a lot of money. In California, if your side project is making a lot of money, you should probably expect to get hit with a lawsuit for misappropriation of trade secrets, etc., because that's what people do when money is on the table. It is of course true that the vindictive or psychotic boss could always try to make your life a living hell by filing a ridiculous lawsuit, but if they want to do that, they'll do it no matter what state you live in, and just trudge up whichever allegations seem most plausible. California's toting of such protections is really a crafty political scheme. The change in law doesn't really make a substantial material change for anyone, as it's almost never worthwhile to sue someone over their side project (and if it is, you can usually get them on all kinds of violations that are related to but are not directly "he was employed by me while he made it"), but it sounds great in a soundbite and gives the people something to feel better about when they look at their tax rates. Aside from these "protections", the state has significant disadvantages for someone interested in running a side project or any other type of business, not the least of which are the high taxes.