The Supreme Court struggled with the changed world of retirement plans Monday, trying to decide whether a worker has a right to sue to recover losses when his instructions on where to invest his retirement money are disregarded.

The justices debated the case of James LaRue, who says he lost $150,000 in a market downturn when administrators at his 401(k) retirement plan twice failed to carry out his requests to sell stocks and move his money into safer investments.