No area previously set aside permanently has ever been reopened to drilling.  Bush undid a Clinton-era reservation, but it was a temporary, 20 year reservation which was going to expire anyway in 2012, Bush in effect cut it short by 4 years. the law does not grant a future president the authority to undo permanent  reservations. If Congress does not explicitly authorize something in giving authority to the president, the president cannot do it Like the Antiquities act being a 1 way power, the president may reserve areas under OSCLA, but may not un-reserve them