starstarstarstar-half(3.5 stars)

Within days of his inauguration, President Trump issued an executive order that suspended immigration rights for Syrian refugees and prohibited citizens from seven mostly Middle Eastern countries from entering the United States.

What became known as the “Muslim ban” would be one of the most defining and notorious watersheds of the Trump administration. And its rollback is rivetingly portrayed in “The Fight,” an artfully crafted and improbably entertaining documentary about the American Civil Liberties Union. Viewers expecting a plodding and self-righteous tutorial on American jurisprudence are instead invited to witness, firsthand, the litigation of four hallmark cases in which ACLU attorneys attempt to preserve immigration rights, reproductive freedom, the ability of transgender individuals to serve in the military and voting rights — in one case, all the way to a young lawyer’s first appearance before the U.S. Supreme Court.

Although the Muslim ban episode kicks off “The Fight” and skillfully establishes context and highly pitched emotional stakes, it is not the film’s primary focus. Instead, the filmmakers proceed to follow ACLU attorney Lee Gelernt, a rumpled veteran who is battling Trump’s family separation policy, which for the despondent woman he’s representing means she hasn’t seen her young daughter in months. Brigitte Amiri, deputy director at the ACLU’s Reproductive Freedom Project, has taken on the case of a teenager from Central America who has been barred from receiving an abortion in Texas. Chase Strangio and Joshua Block are challenging Trump’s attempt to ban trans people from serving in the military. And Dale Ho is trying to remove the citizenship question on the upcoming U.S. census.

Gracefully toggling between these disparate but related cases, “The Fight” portrays its protagonists as superheroic Davids doing battle with a looming, largely unseen Goliath. Afforded unprecedented access to the ACLU’s offices and inner workings, the filmmakers have created a portrait of idealism and hard work that might be mistaken for a promo piece for the organization’s 100-year anniversary, which it’s celebrating this year. Still, directors Elyse Steinberg, Josh Kriegman and Eli B. Despres (who made the equally engrossing 2016 documentary “Weiner”) have found real-life characters who are every bit as pluralistic and paradoxical as the American citizens they represent. What’s more, they are on the scene when the ACLU decides to advocate for the white supremacists marching in Charlottesville in 2017, a move that’s met with outraged dissent within the ranks.

If “The Fight” gives short shrift to the contradictions embedded within the ACLU’s mission — defending the Constitution at its most distasteful, offensive and reprehensible edges — the film is exceedingly well-made, making arcane legal theory legible and comprehensible, maintaining a swift and engrossing pace and getting inside inaccessible courtrooms by way of stunning animations directed by Arvid Steen.

Most impressively, Steinberg, Kriegman and Despres follow just the right people to give the audience a candid and often amusing glimpse of the workaday life of an ACLU attorney, whether it’s Amiri celebrating a victory with “train wine” on Amtrak (where she seems to live half her life) or Ho tensely rehearsing for and then nervously awaiting the results from an argument at the Supreme Court. The unintended star of “The Fight” might just be Gelernt, whose hilarious bouts of technophobia punctuate what is easily the film’s most heartbreaking case. In this engrossing and ultimately inspiring examination of ideals in action, the team behind “The Fight” wind up illustrating a cardinal rule of nonfiction filmmaking: When it comes to humanizing even the loftiest principles, a documentary lives or dies by its principals.

PG-13. Available on demand at various streaming platforms, including theavalon.org and jxjdc.org. Contains strong language, mature thematic material and brief violence. 96 minutes.