Legal Question in Family Law in California

Legally, yes, but probably not really. Absent a qualified change in family circumstances, I know of no insurance plan that will allow you to add or remove dependents from the plan except at open enrollment time. Until he files there is no change, and once he does he's under an automatic court order not to drop any insurance (along with a lot of other automatic restraining order terms). In addition, it would only be temporary, because once the divorce papers are filed, the wife will be able to easily get an order that the husband cover her and the child pending the divorce proceedings, and cover the child even after the divorce. Lastly, it could turn out to be a really stupid move if the wife or child gets seriously sick or injured, because the husband will be responsible for the wife's medical bills until the divorce is filed, and may be ordered to contirbute to them out of community assets and/or spousal support after, and he will be responsible for the child's bills jointly and severally with the wife until the child is 18 and graduates from or drops out of high school.

At the time you file the divorce petition, you should be filing a motion to address (among other things) the reinstatement of the insurance if in fact wife and child were removed from coverage.