You can however, re-list the proeprty with a new agent and then you will owe the first agent nothing.
Since you home did not sell you should try to consider working with another agent.
Moreover, aren't you still in need of the services your Realtor will provide? Are you prepared to negotiate the contract, arrange the inspection, the appraisal, make sure the buyer follows required timelines, etc? Will you have to pay a lawyer instead?
In the event you still feel like treading the much more legally treacherous road, please get the opinion of a lawyer regarding the state of your contract with your former Realtor.
Mortgage Broker responds...
You probably can, but is it right? I say NO!
I'm not the biggest fan of many realtors, but come on, they're the ones who brought you the buyer, so at least give them 1%!
You agree to give that realtor at least 1% and will agree to make a contribution to the Wounded Warrior Project and I'll agree to disclose to the buyer where they can get some of the best terms for their situation which will better ensure the deal actually closes!