★★★★★

As Ruth Bader Ginsburg celebrates her 25th year on the nation’s highest court, “On the Basis of Sex” focuses on the court case that launched her battle to dismantle legal barriers for women, presenting the origin story of the Supreme Court justice we now know as the Notorious R.B.G.

“On the Basis of Sex” opens with a sea of young men in drab suits ascending the steps for their first day at Harvard Law School, Ruth — played by the elegant Felicity Jones — the only speck of color among them in her vibrant blue dress. This jarring visualization of gender inequality aptly prepares the audience for Ruth’s struggle to succeed in a male-dominated world.

Thus the biopic begins with Ruth’s time at Harvard, complete with not-so-subtle jabs about how the nine women in a class of 500 have usurped spots rightfully belonging to men. The story then follows Ruth’s early years as a professor of gender law at Rutgers University after no law firm will hire her because she is a woman. The only person who believes she can succeed as a lawyer is her unfailingly supportive husband, a tax lawyer named Marty, played by the incomparably genial Armie Hammer.

Marty gives Ruth her first opportunity to challenge the law she teaches about when he brings her a case involving a tax code provision that disadvantages men. Hoping a male petitioner will make her case more persuasive to the male judges, Ruth takes the case to the 10th Circuit Court of Appeals to convince them that any law that discriminates on the basis of gender violates the U.S. Constitution.

Jones’ performance is not flawless — the Oscar-nominated British actress never quite nails the Brooklyn accent — but she nonetheless makes Ruth the emotional backbone of the film. The potency of her facial expressions propels Jones to shine as Ruth, as does the subtle body language that reveals the nuances of her character.

When Ruth listens to the Harvard Law dean talk about what it means to be a “Harvard man,” she lifts her chin ever-so-slightly; without her expression even changing, the audience can feel her rise to the challenge. When she realizes she is about to be turned down for yet another job, this time because the other lawyers’ wives would be jealous of a woman in the office, viewers can see the dimming of her hope through the infinitesimal shift in her smile. Jones’ careful character study exposes the onslaught of microaggressions Ruth endures as a woman in the mid-20th century and compels the audience to feel the weight of them too.

The chemistry between Hammer and Jones is similarly powerful as they establish an impressively equal relationship between Marty and Ruth, atypical of the gender norms of the time. Marty’s willingness to share household tasks like cooking and child care, combined with his unwavering belief in his wife, makes him an ideal husband. Even better, his characterization is a faithful replication of the real Marty, not a Hollywood fictionalization.

Throughout the film, Marty’s belief in Ruth does not rest at mere platitudes to her face; the film weaves in multiple scenes in which he defends her to the many who doubt her, adding to the moving and inspiring tenor of the film. Whether it be the Harvard Law dean, Marty’s boss or Ruth’s own friend at the American Civil Liberties Union, almost every other character questions her ability to be a real lawyer, making Marty’s support ever more significant.

While Marty and Ruth’s touching love story provides the heart of the film, it does not overshadow the evolution of Ruth’s personal character and legal career. As Marty, Hammer plays the rare role of a husband whose characterization revolves around his wife, and he is all the more likable for it. While the film lacks Marty’s own storyline or development, this absence is forgivable in light of this refreshing dynamic.

One of the film’s greatest triumphs is its marrying of Ruth’s personal and professional lives. The filmmakers effectively weave scenes of the prosecution grumbling in dimly lit rooms about working women destroying the American family with scenes of Ruth and her family.

As the prosecution declares that women who work neglect their children, for example, Ruth shares several emotionally charged scenes with her daughter, Jane, played by Cailee Spaeny. Through their shared moments on screen, we see how Ruth’s love for her daughter fuels her desire to undo the blockades she has faced her entire career so Jane will not encounter the same ones. The film masterfully undermines the claim that women cannot balance their family and a job and highlights the generational impact of Ruth’s work.

Just as family is central to the plot of the film, it also drove the creation of the film. “On the Basis of Sex” was written by Ruth’s nephew, Daniel Stiepleman, who was inspired by a eulogy given at her husband’s funeral in 2011, according to The New York Times.

Ruth’s oral arguments in court at the end present the culmination of her self-doubt and frustration after others have relentlessly asserted her inability to change the world. These scenes inject tension and suspense into the film as Ruth tries to convince a federal court that the law must reflect the cultural shift of their country. As she urges them to stop protecting an America that no longer exists and set a new legal precedent, the film reveals the fiery Ruth who had previously only come through in flashes of defiance.

This biopic succeeds in delivering a small piece of history with a critical effect, but it excels in investing the audience in its characters — particularly Ruth, the focal point of the film. The window it provides into Ruth’s life casts a shade of vulnerability and adversity over a woman we now know to be tough and stoic.

“On the Basis of Sex” is a love letter to Ruth Bader Ginsburg that proves as enjoyable and momentous as the woman herself, complete with a cameo of the legend at the end.