Sudanese president Omar al-Bashir has been travelling freely around the world despite an eight-year-old international warrant for his arrest on charges of war crimes and genocide, human rights lawyers have found.

A project to document the travels of Bashir has called in question a key component in international law after repeated failures to arrest him.

In 2009 and 2010 Bashir was indicted by the Hague-based International Criminal Court on multiple counts of genocide, crimes against humanity and war crimes. Warrants for his arrest were issued on the basis of his “individual criminal responsibility” for those alleged crimes during the conflict that began in Darfur in 2003. However, despite these warrants, in the last decade he has made 150 trips to countries including China, South Africa, Saudi Arabia, Egypt, Jordan and Kenya, with many of these party to the statute that set up the ICC.

Human rights lawyer Oliver Windridge, who previously worked at the international criminal tribunals for Rwanda and the former Yugoslavia, set up the Mapping Bashir project to see if the indictments had any impact on Bashir’s movements.

Working with Professor Michael A Newton from Vanderbilt Law School, he has documented all of Bashir’s trips overseas, as well as those that were cancelled. “There’s a lot of legal theory about whether a head of state enjoys immunity from arrest, and whether that immunity is trumped by certain kinds of offences,” said Windridge, citing those such as genocide, war crimes and crimes against humanity. “By looking at Bashir’s travels while ICC arrest warrants are outstanding, we hope to begin to understand the effectiveness of these warrants, particularly against sitting heads of state, the limitations of international tribunals and the need for global compliance. It is indisputable that, to date, the ICC’s arrest warrants have not achieved their objective: the arrest of Bashir.”

Since the indictments, Bashir has made regular trips to countries that are not full members of the ICC, such as Saudi Arabia, Ethiopia and Qatar, but it is his visits to full members of the Rome statute, such as South Africa, Uganda and Jordan, that raise the most questions. This was highlighted when Jordan was referred to the UN security council by the ICC following its failure to arrest him during a March 2017 trip. Jordan’s response was that he was immune from arrest as a sitting head of state. Jordan said it subscribed to the need to punish those responsible for crimes within the court’s jurisdiction, but not at the “expense of fundamental rules and principles of international law aimed at securing peaceful relations among states”. South Africa was also admonished for similarly failing to arrest him, but the ICC decided not to refer it to the UN.

The Bashir case goes to the heart of the problem with the ICC, Windridge said. There are 123 countries signed up, but the lack of a police force means it is reliant on countries implementing its decisions.

“How useful is the ICC when it can’t arrest those it wants to try for crimes they have allegedly committed?,” asked Windridge. “[Bashir] is consistently travelling to non-state parties, which is undoubtedly frustrating, but of more concern is that he is also consistently travelling to state parties, sometimes on multiple occasions,” he said. “And it does appear that one of the biggest weaknesses the ICC faces in this case and moving forward is arresting sitting heads of state, which is concerning, as eradicating immunity was one of the very reasons the ICC was created.

“It wasn’t created to try low-level perpetrators, it was created to try those most responsible for the worst crimes, when domestic prosecution could not take place. But those most responsible are often those leading countries, and we are having great difficulty actually prosecuting them.”

Having gathered the data, the Mapping Bashir team have also been able to show when he cancelled a planned trip, which happened 23 times over the same time period.

The number of trips peaked in 2015 when he made 27, followed by 24 in 2017 and 23 in 2016.

Despite the gloomy picture of how effective arrest warrants can be, Windridge says the court can operate successfully. But he accepts the project raises more questions for the international community than it answers. “Mapping Bashir is a valuable project and it can work to assist the ICC and others, but there is concern about how you put what we are finding into practice, at the state level,” he said.

“Is the reality that the ICC will only ever try former heads of state, those deposed from power? It’s possible, but many people would say that isn’t a good place to be, nor is it the ICC vision that so many worked hard for so many years to create.

“The idea was, and continues to be, that if a wanted person were to leave their country and go to an ICC member state, they would be arrested. So in a sense, at the very least, they would be pinned into their own country with very limited or no travel, becoming an international pariah.

“But what we are seeing with Bashir is quite the opposite and we are now seeing the realisation that arresting and trying sitting heads of state is a lot more complicated than perhaps first thought.”