Karzai administration blocking corruption investigations
It appears to me the obvious answer to this problem is to charge those who giving the orders to remove names from investigations with obstruction of justice and prosecute them. That is probably the only way you will stop the practice.
Top officials in President Hamid Karzai's government have repeatedly derailed corruption investigations of politically connected Afghans, according to U.S. officials who have provided Afghanistan's authorities with wiretapping technology and other assistance in efforts to crack down on endemic graft.
In recent months, the U.S. officials said, Afghan prosecutors and investigators have been ordered to cross names off case files, prevent senior officials from being placed under arrest and disregard evidence against executives of a major financial firm suspected of helping the nation's elite move millions of dollars overseas.
As a result, U.S. advisers sent to Kabul by the Justice Department, the FBI and the Drug Enforcement Administration have come to see Afghanistan's corruption problem in increasingly stark terms.