Pettersson's documented professional life is rooted in Sweden. His legal education took place at Uppsala University, and his career unfolded in Stockholm, the country's largest legal market for business law firms.
His practice centred on the European Union and competition law, an area that grew in importance for Swedish and international companies as EU rules shaped national business regulation.
Pettersson studied law at Uppsala University and completed his degree in 1985. Founded in 1477 through a papal bull, Uppsala University is the oldest university in Sweden and the oldest in the Nordic region.
Its early teaching centred on philosophy, law and theology. The university was suspended in 1515 and reopened in 1593, and it expanded considerably during Sweden's rise as a great power in the seventeenth century.
Pettersson spent about 25 years as a partner at Mannheimer Swartling, the Stockholm-based business law firm. The firm was formed in 1990 through a merger between Mannheimer & Zetterlöf, founded in Gothenburg in 1943, and Carl Swartling Advokatbyrå. Today it is regarded as the leading business law firm in the Nordic region.
He co-chaired the firm's EU and competition practice group and is credited with founding its Brussels office. His work included counsel for Swedish and international clients in competition proceedings before Swedish courts, the EU courts and arbitration tribunals, as well as cartel and abuse-of-dominance investigations by the European Commission.
In 2018 he joined Setterwalls, whose history dates back to 1878, when the lawyers Nils Setterwall and Oscar von Koch acquired a Stockholm legal practice. The firm, which has offices in Stockholm, Gothenburg and Malmö, was recruiting him to strengthen its EU and competition work, including state aid, and he also brought experience in transactions and litigation.
Since 2020 he has been a partner at Per Karlsson & Co, a Stockholm firm founded in 2019 by Per Karlsson that concentrates on EU and competition law. Pettersson has also written numerous legal articles on these subjects and is a sought-after speaker in the field.
Pettersson co-chaired the EU and competition practice group at Mannheimer Swartling and is credited with founding the firm's Brussels office. Competition law, EU law and state aid were central to his practice, including cartel and abuse-of-dominance matters before the European Commission and national competition authorities.
Pettersson is a member of the Swedish Bar Association, the professional body of lawyers admitted as advokat in Sweden. Nils Setterwall, whose name is attached to the firm Pettersson later joined, was one of the founders of the association in 1887.
He is also a member of the Swedish ICC Competition Committee, the Swedish national committee linked to the International Chamber of Commerce, a global business organization.
