Secondary market participants are once again urging government regulators to revise pending margin requirements for the to-be-announced MBS market, lest they negatively disrupt the space and possibly raise the cost of providing mortgage credit. At issue is SR-FINRA-2015-036, a proposal from the Financial Industry Regulatory Authority to establish margin requirements for the TBA market under FINRA Rule 4210. Previously, the Securities Industry and Financial Markets Association urged...