The fiscally responsible thing to do is apply existing housing toward future housing, and leave retirement accounts untouched and available for retirement. It is irresponsible to dip into 401ks or IRAs INSTEAD of using existing home-equity. Were it I, I'd want to split retirement, leaving it in place for it's intended purpose, and split (either by sale or financing a buyout) the housing and applying my half toward my housing needs.
One cannot live inside a retirement account. The 401k and IRA was CREATED for the purpose of allowing pretax money to grow untouched for future retirement. Most of us will never see a pension. THus, those 401K retirement funds play a vital role and it is nothing short of financially irresponsible to treat a 401k as a savings account. If they have, say 150k equity in housing, they should each get half of that and half of retirement, but left in retirement. If judges are making orders that require cashing out 401ks, rather than splitting available housing monies, SHAME on them for such fiscal short sightedness. Non-retirement money is a different animal than is retirement money, and should be treated accordingly.