Groups including Intertanko, which represents about 80 per cent of the world's tanker fleet, and Lloyd's Register asked the region's top court to review the legality of the EU rules.
The legislation criminalises intentional, reckless and 'seriously negligent' discharges of pollution.
Shipping organisations claim this creates a lower threshold of liability than existing laws on pollution prevention.
The EU law departs from international rules 'by conscious choice', the shipping groups argue in court documents.
EU regulators explained the need for 'further dissuasive and proportionate penalties' by saying that international maritime standards are regularly ignored.
The EU law was partly introduced in response to oil spills off Spain's north-west coast, by the sinking of the tanker Prestige in 2002, and along France's Atlantic coast, by the sinking of the tanker Erika in 1999.
The shipping groups, which also includes the Greek Shipping Cooperation Committee, said the law increases confusion about environmental standards. They won the support of the British tribunals to take their case to the Luxembourg-based European Court of Justice.
'A muddle from beginning to end,' is what Christopher Greenwood, the lawyer for the shipping associations, said about the law before the High Court in London in 2006.
The law is 'a unilateral measure' that breaks away from the 'carefully designed body of international law', he said.
The London tribunal decided to refer the case to the EU court to advise how the bloc's 27 nations should implement the EU rules into their national laws.
Without such guidance, 'there may be a danger of different states implementing the directive in a different manner', the court said in June last year.