Updated from April 20 The proposed marriage of private equity firm Blackstone ( BX ) and credit card services provider Alliance Data Systems undefined, after a nearly yearlong and often tumultuous engagement, has been officially called off. Shares of ADS were dropping 7.1% to $49.07 in premarket trading Monday. Dallas-based ADS issued a statement Friday evening in response to a termination notice it says it received from Blackstone earlier that day. ADS argues that Blackstone has no right to terminate the $6 billion-plus deal to acquire ADS because Blackstone is in breach of the original contract. "The Blackstone affiliates breached their contractual obligations by, among other things, refusing to accept reasonable and customary regulatory requirements and prolonging negotiations with regulators," ADS said. And having established its case, ADS did the breaking up itself: "For these reasons, Alliance Data today terminated the merger agreement."