U.S. District Judge Ralph Beistline refused to end BP's probation, imposed in 2007 for violations of the Clean Water Act, the Anchorage Daily News reported. Federal prosecutors argued the British oil giant's criminal negligence caused the 2009 rupture.
Beistline said mistakes by BP employees preceded the 2009 spill of 15,000 gallons of crude oil. The spill contaminated a stretch of frozen tundra.
"It is incumbent upon BP to make sure this does not happen again," the judge said.
Federal prosecutors argued the 2009 spill was a violation of the terms of BP's probation. They asked the judge to revoke the company's probation, and then to reimpose it with stricter conditions.
Beistline heard several days of testimony before making his decision.