Arbitration clause in a contract executed prior to the entry into force of the new Brazilian Arbitration Act. Subsequent contractual amendments executed after the Brazilian Arbitration Act that do not modify the arbitration clause and expressly state that unaltered clauses would be ratified. Interpretation of these amendments to the effect that the arbitration clause remains subject to the "ultractive effect" of the regime predating the 1996 Brazilian Arbitration Act. Possibility of filing a lawsuit to resolve a dispute arising from the contract: