From the article:
Acting Police Chief Andrew Kirkland said Tuesday the U.S. Attorneys Office in Portland asked for city police cooperation last week. He said police denied the request, citing an Oregon law that says no one can be questioned by police unless they are suspected of being involved in a crime.
You have to at least acknowledge that the police can "interview" people who can reasonably expected to have "knowledge" of a crime, even if they have no involvement.
You also have to acknowledge that immigration and citizenship violations ARE crimes. So the chief's position is indefensible even by his own BS standard.