A constitutional crisis occurred in The Gambia following presidential elections in December 2016, in which challenger Adama Barrow achieved an upset victory over longtime incumbent Yahya Jammeh. It eventually concluded after a military intervention by the Economic Community of West African States (ECOWAS) led to Jammeh's departure from the country.

Although Jammeh first accepted the victory of Adama Barrow on 1 December, he rejected the election results days later. Jammeh called for the election to be annulled, and appealed to the Supreme Court, which refused to rule on the matter. He then deployed troops to the capital of Banjul and the city of Serekunda. The National Assembly, where Jammeh's Alliance for Patriotic Reorientation and Construction held an absolute majority, used emergency measures to extend Jammeh's rule.

The United Nations and ECOWAS, which The Gambia joined under Jammeh's rule, called on him to step down. After he refused, ECOWAS assembled a coalition of military forces from Senegal, Nigeria, and Ghana to intervene in The Gambia using special provisions in the organisation's charter. Jammeh's term was initially scheduled to end on 19 January, and Barrow was sworn in as President of The Gambia in his country's embassy in Senegal. At his request, ECOWAS troops entered the country that day without resistance of the National Army or the National Guard. The Navy explicitly recognised Barrow as president. ECOWAS troops reached Banjul on 21 January, and Jammeh left the country to exile in Equatorial Guinea. Barrow arrived to The Gambia as president on 26 January.

Initial reactions Following the announcement of the results of the elections, opposition supporters widely celebrated the surprise victory and were stunned by Jammeh's concession of defeat. Thousands of people celebrated in the streets of Banjul. However, some expressed caution about what Jammeh might do next – suggesting that he could still try to retain power despite what had happened. A businessman said "I will only believe it when I see him leaving state house. He still controls the army, and his family are the top brass."

A few days after the election, 19 opposition prisoners were released, including Ousainou Darboe, the leader of Barrow's United Democratic Party. Darboe had been arrested in April 2016 and sentenced to three years in prison, and his arrest had led to Barrow's candidacy.

Interviewed shortly after the election, Barrow thanked the Gambian people, including those in the diaspora outside of the country, and appealed to them to put aside their differences and work together for the development of their country. He said, "I know Gambians are in hurry but not everything is going to be achieved in one day. I would therefore appeal to all Gambians and friends of the Gambia to join us and help move this great country forward. I don't want this change of regime to be a mere change. I want it to be felt and seen in the wellbeing of the country and all Gambians. So we are calling on all Gambians and friends of the Gambia to help us make the Gambia great again."

Barrow said his early priorities include helping the agriculture sector. He said "We don't have minerals here. The backbone of this country is agriculture. ... Under President Yahya's government, all those farming centres collapsed completely, and they no longer exist." Asked about his plans for judicial reform, he said "We want a free and independent judiciary whereby nobody can influence the judiciary. We will put laws in place to protect those people running the judiciary. They will have that job security, they will have that independence. We will reduce the powers of the president."

Jammeh rejects results On 9 December 2016, Jammeh appeared on Gambian state television to announce that he had "decided to reject the outcome of the recent election" due to "serious and unacceptable abnormalities ... during the electoral process". He said that a new election should be held under "a god-fearing and independent electoral commission". The announcement came after Fatoumata Jallow-Tambajang, the chair of the opposition coalition, called for Jammeh's prosecution within a year after the handing over of power in January 2017, and said "We are going to have a national commission for asset recovery" to obtain the return of money and property from Jammeh and his family.

By 10 December, the military of the Gambia was deployed in key locations in Banjul, the capital, and set up sandbagged positions with machine guns, although they were just waving the citizenry through the checkpoints. Troops were also deployed in Serekunda, the Gambia's largest city. The Guardians African correspondent speculated that the prospect of prosecution under a new government might have led security and military leaders to back Jammeh. An attempt by Economic Community of West African States (ECOWAS) chair and President of Liberia Ellen Johnson Sirleaf to negotiate a resolution to the dispute failed when Sirleaf's plane was not allowed to enter the country.

Jammeh's party, the Alliance for Patriotic Reorientation and Construction (APRC), said it would follow up Jammeh's statement by petitioning the Supreme Court to invalidate the election results, meeting a 10-day deadline established by law for contesting an election. There is currently a Chief Justice of the Gambia, but there has not been an active Supreme Court in the country for a year and a half (since May 2015), and it was thought that at least four additional judges would have to be appointed in order for the Supreme Court to convene to hear the case. According to human rights groups interviewed by Reuters, Jammeh wields considerable influence over the courts. Of the three Chief Justices between 2013 and 2015, one was jailed, another was dismissed, while the third fled the country after acquitting someone whom Jammeh had wanted to be convicted. Alieu Momarr Njai, the head of the elections commission, said that if it went to court, they would be able to show that the final tally was correct.

On 13 December, security forces took over the offices of the election commission and prevented the chief of the commission and its staff entering the building. The APRC submitted its appeal seeking the invalidation of the results. Meanwhile, the four regional leaders sent by ECOWAS met with Jammeh but left without an agreement. The military ceased its occupation of the electoral commission's offices in late December and the government said that its staff was free to return to work. It said that the occupation was intended to prevent an attack on the building. It also called for calm and said that daily life should continue as usual. In his 2017 New Year address, Jammeh furiously criticized the position taken by ECOWAS, saying that "it is totally illegal as it violates the principle of non-interference in the internal affairs of member states" and "is in effect a declaration of war and an insult to our constitution". He vowed that he was "ready to defend this country against any aggression and there will be no compromise for that".

Domestic reactions

On the same day as Jammeh's rejection of the results, Barrow said that Jammeh did not have the constitutional authority to nullify the vote and call for new elections, arguing that only the Independent Electoral Commission could do that. Barrow said he had moved to a safe house for protection. According to supporters protecting Barrow's residence, the police and military of the Gambia had declined to protect the president-elect. The third candidate in the election, Mamma Kandeh, also called on Jammeh to step down, saying "Your swift decision earlier to concede defeat and your subsequent move to call Adama Barrow to congratulate him was lauded throughout the world. We therefore prevail on you to reconsider your decision."

On 12 December, the Gambia bar association held an emergency meeting. They called Jammeh's rejection of the election results "tantamount to treason" and passed a unanimous resolution calling for the resignation of the Chief Justice of the Supreme Court, Nigerian judge Emmanuel Oluwasegun Fagbenle, for gross misconduct, saying he had shown a lack of independence and impartiality by campaigning for Jammeh and inappropriately interfering with decisions made by judicial officials. The Gambia teachers' union called Jammeh's action "a recipe for chaos and disorder which undoubtedly endangers the lives of all Gambians particularly our children". The Gambia Press Union, the University of the Gambia, and the country's medical association and Supreme Islamic Council also supported the view that Jammeh should step aside and allow Barrow to assume the presidency. On 20 December, twelve serving Gambian ambassadors sent a congratulatory letter to Barrow and called on Jammeh to step down. In response, Jammeh's new Information Minister, Seedy Njie said on 10 January 2017 that the twelve ambassadors had been fired.

On 13 January, Barrow said that Jammeh should not seek asylum in Nigeria, which had been suggested by some MPs in the Nigerian Parliament. President Buhari of Nigeria continued trying to negotiate a peaceful end to the impasse. Barrow also stated that he would still be inaugurated on 19 January, despite the dispute. Talks aimed at ending the crisis ended without agreement on 14 January, prompting the African Union (AU) to state that it would no longer recognise Jammeh as president of The Gambia after 19 January. Barrow was instead invited to a regional summit in Mali to further discuss the transition of power. Barrow himself went to Senegal in the days before his inauguration, due to concerns for his safety. He also suffered a personal tragedy during this period when his 8-year-old son died after being bitten by dogs. Barrow missed the boy's funeral on 16 January 2017, as he did not feel safe to return to The Gambia to attend.

International reactions Jammeh's action was condemned by the governments of the US and Senegal. The AU also declared that Jammeh's actions were "null and void". After Senegal called for an emergency United Nations Security Council (UNSC) meeting, the UNSC declared in a unanimous statement that Jammeh must peacefully hand over power.

It was announced that a delegation of four West African heads of state planned to go to The Gambia on 13 December to try to persuade Jammeh to accept the results of the election and step down. These included the President of Liberia and chair of ECOWAS Ellen Johnson Sirleaf, the President of Nigeria Muhammadu Buhari, the (outgoing) President of Ghana John Mahama, and the President of Sierra Leone Ernest Bai Koroma. The African Union said it also planned to send a negotiating delegation to The Gambia, led by President of Chad and chair of the AU Idriss Déby. Federica Mogherini, the High Representative of the European Union for Foreign Affairs and Security Policy, issued a statement saying that the European Union requested Jammeh to respect the outcome of the election and step down, and that "Any attempt to reverse carries the risk of serious consequences." Samantha Power, the United States Ambassador to the United Nations, said "It is a very dangerous moment."