On January 23, the International Court of Justice issued a unanimous ruling that ordered Myanmar to “take all measures within its power” to protect its ethnic minority Rohingya population from genocide. The case — against which Myanmar’s civilian leader, Aung San Suu Kyi, argued unsuccessfully — ended up in front of the ICJ because of a tiny African country thousands of miles away. Here’s what you need to know about this story.• How the case got startedThe case before the ICJ started a few weeks ago, when Gambia accused Myanmar of violating the United Nations’ 1948 Convention on Genocide. Suu Kyi flew to The Hague to defend her country, arguing that her government’s actions were legitimate counterinsurgency efforts against rebels in Rakhine state.Gambia requested immediate measures to prevent further harm to the Rohingya. Last week’s ruling was the ICJ’s response. The ICJ has not yet ruled whether genocide has been committed. The court demanded that Myanmar report back within four months on what steps it has taken and preserve any evidence relevant to the genocide case.Since 2017, about one million Rohingya have fled a campaign of violence orchestrated by Myanmar’s security forces. These attacks come after decades of discrimination and persecution against the Rohingya, a Muslim minority in Myanmar, where they have been denied basic citizenship rights. In 2018, a UN fact-finding mission called for senior generals of the Myanmar military to “be investigated and prosecuted in an international criminal tribunal for genocide, crimes against humanity and war crimes”.• What is the International Court of Justice?The International Court of Justice is the United Nations’ highest court. Also known as the World Court, the ICJ primarily settles interstate legal disputes with the consent of both parties. It is not a criminal court and does not prosecute individuals. Governments agree to abide by the court’s decisions in cases in which they are a party and to carry out provisional measures as the court requests. The ICJ typically has 15 sitting international judges who do not represent their countries. Rather, they must act as international civil servants.The concept of consent is central to the ICJ’s functioning. As defined by Article 36 of the ICJ Statute, governments can consent to a case through three avenues: a case-by-case referral, prior declarations of consent or treaty-based consent. The case of Gambia against Myanmar is based on the latter, as both states are parties to the Convention on Genocide.• Why Gambia?Any of the 152 states that have ratified the Convention on Genocide could have filed the case against Myanmar at the ICJ. So why did Gambia step up?The answer relates to what political scientists Martha Finnemore and Kathryn Sikkink called norm entrepreneurs. The life cycle of a norm starts with a norm entrepreneur using an organisational platform to persuade other actors such as governments and international organisations to accept and adopt the norm.Gambia has long been a human rights leader. In the 1970s and 1980s, the country led continentwide efforts to build the regional African human rights system. Gambia’s president in that period, Dawda Jawara, helped lay out those foundations.When the Organisation of African Unity in 1979 called for a committee of experts to draft a continentwide human rights instrument, Jawara proposed to host the drafters. The group ultimately created the African Charter on Human and Peoples’ Rights, also known as the Banjul Charter. The African Commission on Human and Peoples’ Rights is headquartered in Banjul, Gambia’s capital.Jawara’s norm entrepreneurship was also evident after Yahya Jammeh overthrew him in a military coup in 1994. Jawara filed a case at the African Commission on Human and Peoples’ Rights against the country he had formerly ruled. In May 2000, the commission ruled that the Government of Gambia was violating several provisions of the African Charter. Jawara never returned to power, however. Jammeh took over as president and ruled for 22 years.Jammeh was accused of corruption and human rights abuses and was driven into exile in 2017. With his regime gone, Gambia is resuming its leadership on global human rights. This time, the effort is spearheaded by Abubacarr Tambadou, the country’s justice minister. “The fact that no one, no one helped us, no one put pressure on President Jammeh to stop his atrocities, that has led us to go through a very difficult two-decade period. We don’t want others to feel our pain or our fate,” he told the PRI-BBC programme The World.Tambadou was a prosecutor at the UN tribunal for Rwanda and quickly drew parallels between Rwanda’s 1994 genocide and what he witnessed in the case of the Rohingya. Tambadou took it upon himself to bring Myanmar to court, with the support of the Organisation of Islamic Co-operation.• What’s next?Gambia has asked the court to condemn Myanmar for violating the Genocide Convention, but adjudicating that request could take many years. Proving genocide requires meeting a very high threshold; prosecutors must show there was intent to destroy a population in whole or in part.Expecting the ICJ ruling, the Myanmar Government appointed a panel that has found that war crimes did take place during the 2017 anti-Rohingya campaign — but the Government denies any “genocidal intent”. Myanmar has refused entry to UN investigators, making it difficult for them to gather evidence.But for the Rohingya, last week’s ICJ ruling is already a victory. The ruling highlights their treatment by the Myanmar Government and their appalling living conditions in what is the world’s largest refugee camp.When the case was first brought, Rohingya refugees pumped their fists in the air, chanting “Gambia, Gambia!” Watching that reveals how much difference a small country thousands of miles away can make when it decides to defend the humanity of the most vulnerable despite the indifference of much more powerful governments and institutions. When asked why a small country such as Gambia took such a leading role, Tambadou simply replied: “Well, why not the Gambia? ... We are doing this in the name of humanity.”• Oumar Ba (@OumarKBa) is an assistant professor of political science at Morehouse College in Atlanta and the author of States of Justice: The Politics of the International Criminal Court (Cambridge University Press, 2020)