MCAS was required to meet certification requirements: otherwise they would not have used it. But it was not implemented to the performance standard of a safety critical system. Now that two smoking holes have demonstrated beyond all reasonable doubt that MCAS is a safety critical system, it likely cannot meet certification requirments, even with a duplex system implementation.
Which is why, a year after Lion Air and seven months after Ethipian they still don't have a credible fix.
So it becomes political: will the FAA bend, and will EASA accept the compromise?