I don't know exactly what claims you're reacting to, but one perpetual issue for it's neighbors is Cali's tendency to use it's political might to force treaties granting it neighboring state's resources and especially their water. California is a tremendously thirsty state and it has a long history of arranging agreements to give itself it's neighbor's water. In the Colorado Compact, for instance, California not only takes the lion's share, they take anybody else's share if so much as a drop isn't accounted for and took vastly more than that before the SCOTUS came down on them, so much so that at one point Arizona actually briefly commissioned themselves a
brown-water navy to patrol the Colorado river and stop California from stealing all their water.