McCann has dual British and Irish citizenship, and uses an Irish passport. In 1971 he escaped from Belfast's Crumlin Road Prison, where he was awaiting trial for a petrol-bombing at Queen's University.
Prominent drugs trafficker Howard Marks was involved with McCann for several years in smuggling hashish from Afghanistan through Irish ports, specifically Shannon Airport, to the UK via Milford Haven in Wales. He was imprisoned at various times in Germany, France, Canada, Northern Ireland and the Republic of Ireland on drug- or political violence-related matters.
He was described as "possibly the most effective arms supplier" for the IRA in the 1970s. He was arrested in the Republic of Ireland in 1979 on a drugs trafficking charge and held in Portlaoise Prison, but was not convicted.
On 2 March 1991, McCann was arrested in a hotel in Düsseldorf, Germany, under the name of Robert Gustave Baehr. Identified by his fingerprints as James McCann, he was charged with being a member of a criminal gang, with smuggling 1,528 kilogrammes of hashish from Morocco to England in March 1988, and with possession of two false passports and small quantities of cannabis and cocaine. In December 1992, after 21 months on remand, McCann was found guilty of participating in "a criminal gang whose purpose was to traffic in considerable amounts of narcotics" and of possession of false passports and quantities of cocaine and cannabis. McCann was sentenced to three years for the drugs trafficking charge and six months each on the other charges, six of which were concurrent. As he had already served almost half the 42-month sentence in detention, he was released shortly afterwards and traveled to the Netherlands.
Under the name of James Kennedy McCann, he was a member of the Republic of Belarus official delegation to a United Nations Framework Convention on Climate Change conference in The Hague in 2000. A company he was involved in, Greenfield Project Management Ltd, since struck off , had attracted funds in the Netherlands, putatively to build bioethanol plants in Belarus. It collapsed after the Belarus Government withdrew support in 2009 following Greenfield's failure to raise investment finance, leaving debts of at least €3 million. McCann acted as Director of Strategy of this company.
In 2012 the Dutch newspaper, De Volkskrant, exposed Greenfield as a fraud conducted by its chief executive Michael Rietveld and director of strategy James McCann in a comprehensive story. In an article in the Economics section of the paper on Saturday 31 March 2012, Economics Editor Erik Bloem detailed how McCann and Rietveld stole €150,000 from a Belgian investor, took in over €4 million from small investors in the Netherlands, ran up debts of over €3 million to creditors — and walked away when the Belarus government withdrew its support from Greenfield Project Management Ltd, and its project.
The company was registered in Ireland, but not a single penny of the substantial sums it took from investors ever passed through the company's accounts or were declared in mandatory annual returns. The Companies Registration Office struck off Greenfield Project Management Ltd from the companies register in 2011, following complaints to the Office of the Director of Corporate Enforcement and a filing by the company's former auditors that its accounts were suspect.
The Dutch public prosecution service and the FIOD (Financial Intelligence and Investigation Service, part of the Taxation Authority) spent more than six months investigating the misdeeds of the two directors, but decided they had not enough evidence to pursue criminal charges. McCann is on the run, believed to be living in the south of France, and Rietveld’s whereabouts are unknown. Belgian police continue their investigations into the theft from Mr Janssens.
McCann has used several aliases in the course of his career, the most well-known being "James Kennedy", and has sometimes been known as "Kennedy-McCann" or "Kennedy McCann".
McCann was a major character in the 2010 Howard Marks biopic Mr. Nice, where he was played by David Thewlis.