Gianni Amelio was in his late sixties when he came out as gay a few years ago. The announcement preceded the release of his documentary “Happy to Be Different,” which worked toward an overriding sunniness in contemplating the trials and challenges of being gay in Italy at various points in the 20th century. In turning to a gay-themed narrative project, Amelio narrows the focus and dims the mood: “Lord of the Ants” takes as its subject the gay Italian author Aldo Braibanti, and the social and legal opposition he faced over his sexuality in mid-1960s Rome. Solemn, stately and perhaps a little stifled, it’s the kind of queer statement you might expect from a veteran filmmaker who wasn’t until relatively recently out and proud, and is rather poignant for that.

In a key scene, the middle-aged Braibanti (played with urbane grace by Luigi Lo Cascio) takes his twentysomething lover and protege Ettore (Leonardo Maltese) to a private party hosted by an elder statesman of Rome’s gay glitterati. “Why all that excess?” asks the young man, professing himself baffled by guests’ brashly flamboyant dress and behavior. “Homosexuals lose all their inhibitions when free from the judgment of other people,” answers his soft-spoken mentor. “I am not like them, but I am like them.” 

Somewhat similarly, “Lord of the Ants” sympathizes with the principle of living out loud while conducting itself a little more demurely. Shying coyly away from the more sensual side of its subject’s life, it concentrates on the quietly righteous academic and political stand that Braibanti took for his sexuality. The bulk of the film takes the shape of an old-fashioned courtroom drama around the absurd, unjust trial he faced in the late 1960s, where he was accused of the medieval crime of plagio — translated as “plagiarism,” or taking possession of another man’s mind for immoral purposes. The sheer legal curiosity of the case, once this deliberately paced film finally gets to it, is compelling, though outside Italy, the film risks falling between two stools: too timid for the LGBTQ market, and too languid for general arthouse consumption.

After some needless chronological zigzagging in the early going, the film’s timeline begins in 1959, with Braibanti ensconced in the artistic commune he has founded in the Emilia-Romagna countryside, where he teaches, stages plays and conducts dedicated research into ant colonies — an ongoing point of fascination in the author’s work, here given some rather clunky metaphorical motivation by Amelio and co-writers Edoardo Petti and Federico Fava. Local youngsters participate in many of his endeavors: Among them, Braibanti finds a particular kinship with Ettore, the sensitive, imaginative youngest son of an oppressively conservative local family.

With his mind expanded and aroused by the older man’s worldly teachings, Ettore cuts ties with his family and accompanies Braibanti to Rome, where their relationship is only intermittently sexual, but marked by mutual tenderness. But the past won’t be so easily left behind, as Ettore’s mother and brother abduct him and set him on a course of conversion therapy that includes ruinous electroshock treatment. Braibanti, meanwhile, is charged with “moral subjugation” of the young man, and the crushing wheels of the midcentury Italian justice system are set in motion. 

As the film enters courtroom drama mode and Braibanti’s case becomes something of a cause célèbre, the script’s focus drifts to enterprising, right-minded journalist Ennio (Elio Germano), who does his best to fight the writer’s corner in the columns of a paper that won’t even print the word “homosexual,” much less defend it. It’s a jarring shift, notwithstanding Germano’s hangdog charisma. With his character so vaguely defined — even his sexuality is unspecified — framing Braibanti’s case through his eyes places the drama in rhetorical terms rather than emotional ones. Meanwhile, Ettore — as winningly played by Maltese, the most rounded and changeable character here — largely recedes from view, until a heartrending scene of plaintive, embittered testimony.

Still, as much as one wishes for Amelio to tell his story with a little more nerve and raw candor — and for DP Luan Amelio Ujkaj to dial back on the yellow filters, which give even the film’s lightest scenes a heavy, gilded air — “Lord of the Ants” is stirring and plangent when it needs to be. A final farewell scene between the thwarted lovers, set to a soaring “Aida” aria sung by Renata Tebaldi, finally hits the grand-scale peaks of feeling and poetry and romanticism that the film has earlier ducked. It ends suffused with the regret and rage that Amelio, as a gay man who endured and survived this repressive era, must recognize and remember all too well.