Mascherano's move had been in some doubt as the players had played for both Corinthians and West Ham within a 12-month period.
A statement from the PL last night reads, "The Premier League is satisfied that the contractual arrangements proposed by Liverpool FC are consistent with its rules; particularly that the relationship between club and player is not subject to third-party influence.
"The Premier League is grateful for Liverpool FC's cooperation and openness at the start and throughout the process.
"Liverpool FC also appreciated the Premier League Board were not prepared to sanction this transfer until further information on any third-party involvement in player registrations had been received from all Premier League clubs."