They have as much authority as they can get away with claiming. Since the president is brazenly defying laws, courts, and the constitution, there’s no reason states shouldn’t push for more autonomy, even if that autonomy may be legally contentious.

But really that’s beside the point. If the state government is too afraid to take a meaningful stand on this, they should focus their attention on other pressing issues instead of passing meaningless laws that make people feel better without materially changing anything.