NEW YORK — A lawyer was ordered to turn over all but $750 of more than $22,000 he collected from clients after a judge determined that he billed the them as much as $450 an hour for time he spent brushing up on basic legal principles.

Gerald and Vivian Kleinerman hired Ronny Buni in March 2011 to represent them in litigation already in progress against their co-operative apartment board. In June 2011, Buni told the Kleinermans that he would not do any more work on the matter, citing an unpaid invoice for $6,239.