Yes, a Judge can deny a reaffirmation agreement even if it is a voluntary agreement between lender and borrower. We discussed the basics of reaffirmation agreements in this post, and we also have posts about car reaffirmations and house reaffirmations. A reaffirmation agreement is, in theory, a voluntary agreement between you and a lender in which you give up the discharge of that particular debt and the lender agrees to keep taking payments and allow you to keep the collateral. Many people in Bankruptcy, especially those who decide to try it without a lawyer, believe that a reaffirmation is required and that idea usually comes from the lender (and occasionally lawyers who do not know what they are doing). As an added level of protection (beyond good advice from a lawyer), Bankruptcy law generally requires that reaffirmation agreements be approved by the court when the schedules reflect that monthly expenses (including the monthly payment at issue) exceed income or the borrower does not have a lawyer.
In the Northern District of Georgia, we have one Judge assigned to hear reaffirmation cases, which makes the process a lot more streamlined and consistent. The Judge is looking out for you, and as you can see by reading the posts linked above, it is often in your best interests to not do a reaffirmation agreement (especially with houses). This is also one of the many hidden traps of Bankruptcy, and unfortunately many people still fall for the advice of a lender who is only interested in getting the money. This is also one of the many reasons a good lawyer will more than pay for him/herself. Entering into a reaffirmation and then defaulting because you cannot afford it means you lose the car or house and you owe the entire debt. That leaves you as bad off as before you filed.