Legal Question in Real Estate Law in California

You are smart to wonder about your liability because, if someone gets hurt on that trampoline, you can be held liable, just because it is partially on your property. You might also be concerned about your homeowner's insurance rates. Sometimes, the premiums increase, when a trampoline is on the property. If you have a trampoline and do not disclose it, you could be denied coverage for a claim or lose your insurance, altogether.

The best way to have the trampoline removed would be to ask your neighbor to remove it. If you are not on friendly terms with your neighbor or the oral request does not work, then the request should be in writing, from you or your attorney. If your neighbor does not remove the trampoline, you can bring an action in court. Esentially, your neighbor has trespassed on your property and has encroached on it. The court action will seek damages for the trespass and encroachment and an injunction, ordering the trampoline removed.

I agree with the previous answer. For various reasons, and with a few exceptions, the law does not encourage self-help in correcting trespasses. If the neighbor won't remove it voluntarily, you'll need to sue. Small Claims seems to be an appropriate venue at the moment - you are limited to asking for money damages and the court cannot issue an injunction-type order for its removal - but it's quick and cheap and the mere bringing of the suit may be sufficient to obtain the neighbor's cooperation.