My Sons wife has asked for a divorce.They have a joint savings account.Can He withdraw 1/2 to open a new acct?

wisconsin is a marital property law state. He has a right to take 50% of the bank account proceeds; however, he should be aware he is also responsible for 50% of the debts and financial obligations, so that is not just free money for him to do whatever he wants with it. The bills still must somehow get paid. Once the divorce gets filed, either party can request an initial first court hearing before the court commissioner and if the parties do not have an agreement, the court will set orders on  support, finances, what bills have to get paid, etc., among other temporary issues.