I haven’t read “The Tribunes” but The Man Who Created Star Trek: Gene Roddenberry by James Van Hise calls it a “futuristic cop show.” What I’ve read about the concept—which was developed for NBC, but not produced—suggests it was not set in the present.
"Futuristic" is ambiguous. It can mean something suggestive of the future, ahead of its time, forward-looking, rather than actually being
in the future. And a lot of "futuristic" sci-fi posits fancifully advanced tech in a present-day setting, e.g.
Search, the bionic shows, or
Knight Rider.
Okay, I found excerpts from the Van Hise book on the Internet Archive. It says on pp. 67-8:
After several years of trying, in 1977 he realized that TRIBUNES, a futuristic cop show, would never go beyond the development stage.
He said, "The police series was intended to have been an effect [attempt?] on my part to show police work as it should be done. It would have shown policemen having to have six years of college minimum, instead of the present academy, and also using the proper scientific method in solving cases. I would have liked to have done it. I think it's too late to do it now because there's already like thirty police shows on and I just don't want to be one of the thirty."
...
The series would have dealt with an experimental police division of 40 to 50 men and women armed with the latest scientific and technological developments. The police no longer carried guns but weapons which splashed high-intensity light temporarily blinding a suspect or spraying nonlethal chemicals.
They are also magistrates, can take testimony, settle cases on the spot, issue subpoenas and the like.
So there are several things there that make me think it was meant to be a present-day or at best near-future series:
One, it was supposed to be an experimental division, something beyond the state of the art for its time. So policing overall is still the same as in real life. Why bother setting it in the future, then, unless it's the very near future?
Two, it used "the latest" science and tech, a phrase suggesting a contemporary setting.
Three, it used basic less-lethal restraint methods like bright lights or chemical sprays, stuff within the realm of current possibility in the '70s, rather than something more sci-fi like phasers on stun. If that was "the latest," then it can't have been very far ahead.
And four, Roddenberry gave up on it because he felt it was too much like all the other cop shows on the air, suggesting that aside from the tech and the methods, the overall feel wouldn't have been that different from a more mundane cop show.
