Legal Question in Real Estate Law in California

The first thing that comes to mind is that you need to discuss this problem with your own landlord. Both aspects of what's going on (carport access and piling tree debris behind your house) are at least to some degree your landlord's problems as well as your own. It sounds to me as though both problems are trespasses and both you and your landlord are adversely impacted to a sufficent extent that either of you could sue. Needless to say, the damages are going to be pretty small, so if this moves beyond the stage of threats and demands, you'd want to tailor it as a small-claims suit. Small claims is quick and cheap, but for the most part is limited to awarding money damages - and with a $7,500 ceiling - rather than giving you an injunction against repeated or ongoing trespass. However, even a token money damages award is likely to deter on-going interference with your, and your landlord's, rights.