A Nigerian court on Friday overturned a request by Nigeria's financial crimes agency to seize an oilfield from Royal Dutch Shell and Eni.
In January, a court had ordered the seizure of the OPL 245 oil block and transfer of operations to the federal government on the request of the Economic and Financial Crimes Commission (EFCC).
Oil companies Shell and Eni had filed motions to dispute this.
The EFCC is investigating whether the $1.3bn purchase of OPL 245 in 2011 involved "acts of conspiracy, bribery, official corruption and money laundering", according to court papers seen in January by Reuters.
"The chairman of the EFCC failed to meet the precondition for making an application for interim attachment of properties. So the application as such was irregular and the order granted on its basis ought to be discharged," Justice John Tsoho of the Federal High Court said.
Gross abuse of power
Shell had said the EFCC conducted "a gross abuse of process and an abuse of power" to get a court order asking for the forfeiture, according to a document obtained by Reuters.
The Nigerian court case is the latest of several inquiries, following those by Dutch and Italian authorities, into the purchase of OPL 245, which could hold up to 9.23 billion barrels of oil, according to industry figures.
The oilfield's licence was initially awarded in 1998 by former Nigerian oil minister Dan Etete to Malabu Oil and Gas, a company in which he held shares.
The licence was then sold for $1.3 bn in 2011 to Eni and Shell. A British court document has shown that Malabu received $1.09 bn from the sale, while the rest went to the Nigerian government.