A/HRC/39/43 9. As a priority, the Group of Experts applied best practices to ensure the safety, security and well-being of witnesses and victims. The present report includes information only where sources granted their informed consent and where disclosure of the information would not lead to any harm. Primary responsibility for protecting victims, witnesses and other persons cooperating with the Group rests with their States of residence and nationality. 10. Consistent with established practice, the Group of Experts applied a “reasonable grounds to believe” standard of proof. 11. Where the Group found information linking alleged perpetrators to specific violations or patterns of violations, such information has been transmitted to the High Commissioner on a strictly confidential basis. In instances where there was insufficient information to identify particular individuals responsible for violations, the party or group responsible has been identified, where possible. 12. The Group of Experts expresses its gratitude to the victims and witnesses who shared their experience. It is also grateful for the assistance provided by government and non-governmental entities and for the support received from United Nations agencies and partners. C. Legal framework 13. Yemen is a State party to 9 of the 13 core international human rights treaties, which remain applicable in periods of armed conflict. The Government retains positive obligations in areas where it has lost effective control. 14. The de facto authorities control large swathes of territory, including Sana’a, and exercise a government-like function in that territory such that they are responsible under international human rights law. 15. Yemen is in a state of non-international armed conflict. In this context, international humanitarian law obligations arise under both treaty and customary law. All parties to the conflict, their armed forces and persons or groups acting on their instructions or under their direction or control are bound by customary international law. Yemen, the coalition forces and non-State actors are parties to the conflict and must abide by the fundamental principles of distinction, proportionality and precaution when conducting hostilities. Moreover, they must ensure that constant care is taken to spare the civilian population, civilians and civilian objects. 16. Yemen is not a party to the Rome Statute of the International Criminal Court, nor are many of the other States involved in the conflict in Yemen. However, many of the Rome Statute’s provisions reflect customary international law. D. Context 17. In 2011, a popular revolution arose against the 33-year rule of Ali Abdullah Saleh, President of Yemen. A deal brokered by the Gulf Cooperation Council granted Saleh immunity and transferred power to Vice-President Abd Rabbo Mansour Hadi. Yemenites conducted a National Dialogue Conference, accompanied by a constitution-making process. In 2014, the conflict escalated between the government forces led by President Hadi, the Houthis and other armed groups over power-sharing arrangements and the draft constitution. In September, the Houthis and the armed forces aligned to former President Saleh seized and consolidated control over the capital, Sana’a and other parts of the country. 18. In March 2015, Saudi Arabia formed a coalition with Bahrain, Egypt, Jordan, Kuwait, Morocco, Senegal, the Sudan and the United Arab Emirates to initiate military action at the request of President Hadi. 1 The United States and the United Kingdom, among other States, advise and support the coalition. The coalition forces launched an air 1 4 Qatar was a member of the coalition until June 2017.