É isso Run Logan (1976)? Da descrição da Wikipedia (ênfase minha):
In the year 2274, the remnants of human civilization live in a sealed city contained beneath a cluster of geodesic domes, a utopia run by a computer that takes care of all aspects of life, including reproduction. The citizens live a hedonistic life but, to prevent overpopulation, everyone must undergo the rite of "Carrousel" when they reach the age of 30. There, they are killed under the guise of being "renewed.” To track this, each person is implanted at birth with a "life-clock" crystal in the palm of the hand that changes color as they get older and begins blinking as they approach their "Last Day.” Most residents accept this promise of rebirth, but those who do not and attempt to flee the city are known as "Runners.” An elite team of policemen known as "Sandmen,” outfitted in predominantly black uniforms and serving in an agency of the city called "Deep Sleep,” are assigned to pursue and terminate Runners as they try to escape.
Os personagens principais, Logan 5 e Francis 7, são Sandmen. No final do filme:
Logan, Jessica, and the other citizens flee the ruined city. Once outside, the citizens see the old man, the first human they have met who is older than thirty, proving that they can, indeed, live their lives much longer.
Para constar, os termos de pesquisa que me levaram a este filme foram filme distópico abate população oficial cidade. (É claro que os resultados da pesquisa são diferentes para todos.) O resultado principal foi Lista da Wikipedia de filmes distópicos, que menciona esse, e o segundo resultado foi a página da Wikipedia para Run Logan si.