Not assisting with enforcement acts you don't feel are worthwhile is not nullification. I'm not engaging in "nullification" when I don't call the police on a jaywalker. Or I mean maybe you think this is, but then police engage in wildcat strikes all the time, or change enforcement priorities, or whatever you want to frame it as. Calling a difference in prioritization "nullification" wrong, especially if local police in immigrant communities want to maintain good relationships with those communities. I think it's laudable that some police forces show an interest in serving their communities interests, as opposed to yearning to be fashy.

> but it becomes very obvious nullification when the state passes laws preventing individuals who would LIKE to help, like local policed departments, from helping even if they wanted to. And this is exactly what has happened in many blue states.

Can you give examples?

Keep in mind, "sanctuary city" policies are usually actually supported by local police forces, because while they may look not tough on crime (and for this reason sometimes police forces halfheartedly lobby against them), they actually make on-the-ground local policing easier, because they engender trust between the local police force and immigrant communities who otherwise might not report crimes at all.