Depending on the terms of the agreement, they may be in breach of contract, which could give you a number of legal options. The consequences of a breach will likely depend on a number of factors, including the settlement agreement itself and the nature of the breach. You may want to consult with a local litigation attorney.
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Failure to honor a mediation agreement brings the dispute of the mediation process and back into the court system unless the agreement has a clause that states that "in the event parties have a dispute arising out of the agreement, they agree to go back to mediation prior to filing anything in court". If your agreement has a mediation clause then a judge will send you back to mediation before seeing you.
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