The South Jakarta district court has ruled that the Indonesian police seizure of the superyacht Equanimity – sought by the US Department of Justice over the 1MDB matter – is invalid.

"We declare the confiscation by police as invalid and legally baseless," Justice Ratmoho was quoted as saying by Singapore's Straits Times.

When contacted, lawyer Andi F Simangunsong, who acts for the owner of the superyacht, said Indonesian authorities must now return Equanimity to the holding company.

"The judge ruled that the seizure was not conducted in accordance to procedure.

"As Indonesia was acting based on the FBI's request, it should have been done through the mutual legal assistance (MLA) process.

"Instead, the police did not go through the MLA and used the ordinary process, which was deemed to have failed in complying with the procedure," he told Malaysiakini.

Simangunsong added that the court ruling cannot be appealed.

Indonesian police, in a joint operation with the US Federal Bureau of Investigation, seized the superyacht off the coast of Bali on Feb 28.

The DOJ is seeking to seize the US$250 million superyacht, which it believes was acquired using allegedly misappropriated 1MDB funds.

In total, the DOJ holds that over US$4.5 billion was misappropriated and laundered through the US financial system, and is seeking to seize US$1.7 billion in alleged ill-gotten assets.

Malaysia businessperson Low Taek Jho, who owns the superyacht, had decried the DOJ's "global overreach" following the seizure.