South Essex Register of Deeds John O’Brien said he has received a green light to withdraw what could be millions of dollars from accounts at Bank of America. O’Brien threatened to pull the money to protest the bank’s participation in the Mortgage Electronic Registration System, or MERS — an organization set up by banks that lets them assign mortgages to new owners without filing related documents at registries of deeds. O’Brien argues banks have used MERS to deny the South Essex registry millions of dollars in fees to which it is entitled.