The wrecks of HMAS Sydney and the German raider Kormoran, both lost in battle 67 years ago, will be afforded permanent protection.
Prime Minister Kevin Rudd said Australia had marvelled at the discovery of HMAS Sydney and the Kormoran in deep water 200km off the West Australian coast earlier this year.
"Now the final resting places of the crews have been permanently protected," Mr Rudd said in a statement on Wednesday.
"For more than 66 years the fate of HMAS Sydney II and HSK Kormoran had been the subject of much public speculation and heartache and the finding gave the opportunity for closure for many families and friends of the crew."
Temporary measures to prohibit unauthorised intrusion into the sites were introduced soon after the vessels were discovered, but both ships will now be protected permanently by law.
"We have now made these measures permanent under the Historic Shipwrecks Act 1976 prohibiting the damage, disturbance or removal of the vessels and their relics and requiring a commonwealth permit to enter the sites," Mr Rudd said.
The government has also taken steps to have both sites added to the National Heritage List.
Services were held around the nation on Wednesday to mark the 67th anniversary of the loss of both ships and honouring the 645 crew on the Sydney and the 78 crew on the Kormoran who lost their lives.