By Peter Busch at CBS News

PHOENIX — CBS 5 News has learned that Phoenix police are investigating one of their own officers for criticizing Arizona’s controversial new immigration law in an Internet video.

The video featuring Officer Paul Dobson appears on Facebook, and in it Dobson says: “This law will make me feel like a Nazi out there,” and, “This law is, pure and simple, a racist law.”Dobson states at the beginning of the video that he is expressing his own personal opinions and not speaking for the city of Phoenix or the police department.

A Phoenix police spokesman confirmed that the department’s Professional Standards Bureau is investigating Dobson for reasons related to the video.That spokesman also said the bureau has not investigated Officer David Salgado or Police Chief Jack Harris for their public criticism of Senate Bill 1070, the immigration legislation.Dobson’s union representative said there appears to be a double standard.”

There is some concern about the consistency and the fairness about how we’re treating this employee versus others that appear to be engaging in similar conduct,” said Joe Clure, of the Phoenix Law Enforcement Association.Sources also told CBS 5 News that the lieutenant who oversees Dobson is hesitant to discipline him because he believes it is a double standard if he is the only one punished.