Law 27 governs insufficient bids. Basically, insufficient bidder's LHO may accept the bid - if he does, the bid is treated as legal, and the auction continues. If he does not, the bid must be corrected by either a sufficient bid or a pass (no doubles or redoubles). If the bid is corrected to the lowest sufficient bid in the same denomination, and both the insufficient bid and the new bid are definitely not conventional, there is no penalty; otherwise offender's partner must pass for the remainder of the auction, and there may be lead penalties.