> "To Serve and Protect," is a phrase made famous by the Los Angeles Police De­partment and adopted, in various forms, by law enforcement agencies across the United States.

https://www.policemag.com/articles/to-serve-and-protect-v2

> In February 1955, the Los Angeles Police Department, through the pages of the internally produced BEAT magazine, conducted a contest for a motto for the police academy. The conditions of the contest stated that: “The motto should be one that in a few words would express some or all the ideals to which the Los Angeles police service is dedicated. It is possible that the winning motto might someday be adopted as the official motto of the Department.”

> The winning entry was the motto, “To Protect and to Serve” submitted by Officer Joseph S. Dorobek.

> On November 4, 1963, the Los Angeles City Council passed the necessary ordinance and the credo has now been placed alongside the City Seal on the Department’s patrol cars.

https://www.lapdonline.org/lapd-motto/

I don't know what film you're referring to, but it's been a motto since the 50's, and made official since the 60's.

We could easily create a duty at the state or local level if we wanted to. The US Constitution is pretty silent on a lot of issues that are remanded to the states.

A mere concuss is never sus!

Maybe a little blood and puss.

Don’t be a wuss![1]

[1] This rhyme only works in certain dialects of British English. For most English speakers, it won’t. It’s a bit like that Nickelback song Never Made It As A Wise Man when he rhymes “story” with “sorry”. Nickelback didn’t realize he developed a moat, an uncompetitive advantage, and nobody would be able to sing his wonderful songs. Nobody, except him.