Lets say Bob and Mary are about to get separated and divorced. Bob has a 401K and a savings account that Mary can not access. To prevent having to give Mary half when they divorce, Bob decides he wants to go a luxurious vacation and spend his hard earned money. Can Mary legally prevent Bob from spending his money?
Mary has two options (that are not mutually exclusive).
The stronger one is to file for divorce immediately and obtain an injunction against this activity in that case. In some states (e.g. Colorado) an injunction takes effect the moment that divorce papers are served upon a spouse.
The weaker one is to ask the divorce judge to allocate the value of the imprudently spent funds to Bob in the division of assets. The doctrine that allows the judge to do this even in a state that otherwise has only "no fault" divorce, is often called "economic waste" or "economic fault." The same doctrine applies, for example, if one spouses destroys valuable property of the other out of spite.