The plan document sucks. Ideally it would say that a participant may specify that all or a portion of a lump sum distribution will be directly rolled over. It has nothing to do with elective or nonelective accounts. The plan provides for lump sum distributions. To me, that means all account balances are distributed at once in "a lump sum." He cannot get a distribution of one source account and leave the other source account in the plan. Look at your document very closely again. If it does not prevent an interpretation that would be in line with the ideal plan terms, then interpret the plan that way. The service provider needs to be on board to handle payment of one portion of the lump sum distribution as a direct rollover and the other portion as a taxable distribution