Area of expertise

  • Dispute Resolution,
  • Energy and Climate Change,
  • Tax

Jan B. Jansen is a prominent and respected lawyer, who specializes in dispute resolution, tax and insurance law, as well as the oil and energy sector.

Jan has worked closely with oil and energy since 1986 and has acted for his clients in many capacities: such as advisor on regulatory matters and transactions, and as counsel in litigation. His clients include many of the largest companies active on the Norwegian Continental Shelf, as well as the Norwegian State. Jan has a thorough understanding of the oil and gas business and the challenges facing the actors involved. He has represented most of the large E&P companies in tax litigation and has successfully pleaded many of the most notable tax cases for the industry.

Additionally, Jan has represented a number of law firms in professional indemnity claim cases. He also assists on insurance matters, where he advises insurance companies on policy issues and claims handling, and represents them in insurance and reinsurance disputes.

As a litigator, Jan acts on a large variety of commercial cases before the courts and arbitral tribunals. He is also sought-after as arbitrator. For many years, he taught General Tax Law and Petroleum Tax Law at the University of Oslo.

Jan was admitted to the Supreme Court in 1997 and has since pleaded numerous landmark cases.

He is head of the Norwegian Bar Association’s Legislative Policy Committee for Energy, Hydropower, Oil and Gas law.

“Jan has a very strong commercial understanding and excellent legal analysis.”

Chambers Europe

Work experience

  • 2010 - present - Partner, BAHR
  • 2001 - 2010 - Partner, Arntzen de Besche Advokatfirma AS
  • 1989 - 2000 - Partner, Arntzen, Underland & Co
  • 1986 - 1989 - Associate and lawyer, Arntzen, Underland & Co
  • 1984 - 1986 - Legal adviser, The Ministry of Finance, The Tax Law Department


  • 1997 - Admitted to the Supreme Court
  • 1984 - Cand. jur, University of Oslo
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