Don and Gillian ordered Olivia that she's off the Vivian Arliss case as she's the guardian of the suspect's son, Calvin. They feared that Olivia could be seen as a Detective who's desperately wanting a family and convince a drug addict to keep Calvin. Olivia denied it. Don and Gillian also ordered Elliot to be off the case.
Elliot: Who's going to accuse me of stealing someone else's kid? I already got 5 of my own
Gillian pointed out that he and Olivia have been partners for over a decade; they have each other's backs and are closer than married couples.