The Guardian Council, a 12-member panel tasked with constitutional matters, backed election law changes that diminishes the authority of the Interior Ministry. Elections will be run by a central panel with members from the three branches of power and seven other figures.
Iranian journalist Roozbeh Mirebrahimi told Radio Free Europe/Radio Liberty the changes are seen as a way to contain Ahmadinejad.
"A major part of the changes were made because of the concerns of the conservative critics of the Iranian president who are worried that Ahmadinejad and his team could try to interfere in the election and influence the results," said Mirebrahimi.
Ahmadinejad is ineligible to run in June elections because of term limits. His re-election in 2009 sparked unrest not seen in Iran since the 1979 revolution.
Ahmadinejad expressed reservations about revisions when lawmakers addressed the issue in December. He fell out of favor with the clerical elite last year and has been subjected to criticism over economic policies.