> California's "sanctuary state" law is a formal rejection of federal sovereignty over immigration.
It is not, since they do not attempt to prevent the federal government from enforcing federal immigration laws in California. They refuse to assist such enforcement in any way - but that is a right that was always implicit in the federal structure of the government, and was made explicit by the courts in Printz v. United States (ironically, it was a 5-4 case split along ideological lines, with the liberal minority arguing in favor of the federal government able to commandeer state law enforcement).
If you want to see an example of actual formal rejection of federal sovereignty, that would be something like the Kansas' Second Amendment Protection Act, which explicitly declares:
"It is unlawful for any official, agent or employee of the government of the United States, or employee of a corporation providing services to the government of the United States to enforce or attempt to enforce any act, law, treaty, order, rule or regulation of the government of the United States upon a firearm, a firearm accessory, or ammunition that is owned or manufactured commercially or privately in the state of Kansas and that remains within the borders of Kansas."
A historical example would be the states' resistance to the fugitive slave laws. For example, here's Pennsylvania specifically targeting slave hunters in 1826:
"If any person or persons shall, from and after the passing of this act, by force and violence, take and carry away, or cause to be taken or carried away, and shall, by fraud or false pretense, seduce, or cause to be seduced, or shall attempt so to take, carry away or seduce, any negro or mulatto, from any part or parts of this commonwealth, to any other place or places whatsoever, out of this commonwealth, with a design and intention of selling and disposing of, or of causing to be sold, or of keeping and detaining, or of causing to be kept and detained, such negro or mulatto, as a slave or servant for life, or for any term whatsoever, every such person or persons, his or their aiders or abettors, shall on conviction thereof, in any court of this commonwealth having competent jurisdiction, be deemed guilty of a felony."
That part of the law was stuck down as unconstitutional. But the very same SCOTUS decision - Prigg v. Pennsylvania - also mentioned that the state could ban its officials and law enforcement from assisting in any way, and that's exactly what Pennsylvania did afterwards.