Exxon Mobil has urged the US Supreme Court to overturn the $2.5 billion (€1.66 billion) in damages for the 1989 Exxon Valdezoil spill off Alaska.
Exxon Mobil's lawyer, Walter Dellinger, told the high court the company has paid $3.4 billion (€2.2 billion) for the spill and cannot be held liable for additional punitive damages under federal maritime law.
"Exxon gained nothing by what went wrong in this case and paid dearly for it," said Mr Dellinger, who argued that the company had no malicious intent or improper profit motive.
But the lawyer for about 33,000 commercial fishermen and others harmed by the nation's worst tanker spill replied that Exxon Mobil for three years had overlooked reports that Captain Joseph Hazelwood had a drinking problem.
A key issue in the case is whether the company can be held liable for the mistakes of Mr Hazelwood, who violated company rules when the Exxon Valdezran aground in Alaska's Prince William Sound in March 1989, spilling about 11 million gallons of crude oil.
The spill spread oil on more than 1,900km (1,200 miles) of coastline, closed fisheries and killed thousands of marine mammals and hundreds of thousands of sea birds.
The 90 minutes of arguments before the high court occurred weeks after the oil company reported the highest-ever quarterly profit for a US company of $11.7 billion.