A Wall Street firm wants to collect a $4 million breakup fee from a banker who never started his job. Judges will soon rule if that's legal.

• Jefferies included a $4 million break-up fee in an offer letter to a banker.
• The Wall Street bank is demanding payment after Dean Decker stayed with Credit Suisse after signing.
• A California appeals court is expected to rule shortly on whether the break-up clause was legal.

A Wall Street bank inserted a $4 million break-up fee into an offer letter and demanded the payment after the employee backed out. Seven years on, a California appeals court is set to rule on whether the fee was legal.