How about the role of rolling out the welcome mat for people who are here illegally, telling them they won't be held to the laws of the land, and then make conflicting comments when the chaos starts. How about telling federal agents to leave who are here to enforce the laws that the gov and mayor ignore. If you don't see that as a problem then again you object to any immigration enforcement.
It is not the role of the mayor to enforce federal immigration law. In fact, he's prevented from doing so, which is why you talk about cooperation.
The mayor's job is to ensure the safety and welfare of its residents. That's all. Do you think it's just a coincidence that virtually every PD in every big city has concluded that "sanctuary policies" are pro-safety? I don't. Because sanctuary policies are basically just this: do not attach immigration consequences to every interaction between a person and the government. That's all. It has nothing to do with condoning law breaking.
For instance: if someone risks getting deported for a traffic ticket, then what's he likely to do if he's caught speeding? Just give himself up and get deported? I doubt it. He is likely to flee, creating a high speed chase. That does not promote safety. That promotes the opposite.
For instance: if there's a criminal act, does it promote or hinder public safety to encourage eyewitnesses to come forward? They will not do so if they think the consequence will be deportation. So if you want GOOD law enforcement, then sanctuary policies are a no-brainer.
For instance: if I hire someone to put a new roof on my house, and someone falls and gets injured, should the ambulance driver be enforcing immigration laws? Oh, you got hurt, you're illegal, let's take you to detention. What incentive does that create? And it's even worse if the police also show up to take people away. Is that helping me be safe? No. All I want is a new roof. Now I have no roof because the cops dragged away the roofers mid-job.
Do you get it? Note also that ICE or CBP has tended not to enforce immigration laws in those contexts, until now. They wouldn't be rolling around just looking for people to nab. That's because nabbing my roofers does not help America at all. It just makes for unfinished roofs.