Exactly why do you think the immigration laws can’t be enforced? The SC let stand a ruling that let Cali not cooperate with ICE - the ruling of the 9th circuit had nothing to do with immigration laws. The immigration laws can be enforced 24/7. Sure, it’s harder this way, but the federal government can enforce everyone of its laws.
“Sure, it’s harder this way......”
That is an understatement, mine may be an overstatement, but if you remove local law cooperation federal efforts will be swamped. ICE relies heavily on Local cooperation to find illegal entrants to the US including some really nasty criminals and gangsters that come into the local legal system.
Those coming to the US illegally will gravitate to areas most permissive to them. They will find ways to get there and local governments help them when they get here.
California has set themselves up as an area where the federal laws on immigration basically don’t apply to them. That is the effect and the intent of not cooperating with ICE. The 9th ruled in their favor and the SCOTUS denied the Petition for certiorari and that means the ruling of the 9th stands.