This post is from Anglican Curmudgeon which you can find here.
An excerpt of the Anglican Curmudgeon post is as follows: “Sub silentio (literally, “under [the cloak of] silence”) is a legal term of art for the technique of a court that, say, wants to accomplish something like the overruling of an earlier case — without having to admit in express words what it is doing. For whatever political or collegial considerations prevail at the moment, the court finds it more “convenient” to stop short of saying what it is doing, while doing it nonetheless. Then, either a few (or even many) years later, the court can “discover”, say, that the case of W. vs. X was in fact overruled, sub silentio, by the case of Y vs. Z.
Courts also understandably shy away from overturning their own prior decisions. As Justices O’Connor, Kennedy and Souter noted in declining to overrule Roe v. Wade in the later case of Planned Parenthood of Southeastern Pa. v. Casey, 505 U.S. 833, 844, 112 S.Ct. 2791, 120 L.Ed.2d 674 (1992), ‘Liberty finds no refuge in a jurisprudence of doubt.”’
You can learn more about this issue here.