Charles W. Penrose says that blood atonement cannot be performed now because the law will not permit it, but someday that will change.
Charles W. Penrose, Blood Atonement as Taught by Leading Elders of the Church of Jesus Christ of Latter-day Saints, reported by John Irvine (Salt Lake City: Deseret News, 1916), 38-39
These are some of the ideas entertained by the Latter-day Saints on the subject of blood atonement. After baptized persons have made sacred covenants with God and then commit deadly sins, the only atonement they can make is the shedding of their blood. At the same time, because of the laws of the land, and the prejudices of the nation, and the ignorance of the world, this law cannot be carried out. But when the time comes that the law of God shall be in full force upon the earth, then this penalty will be inflicted for those crimes committed by persons under covenant not to commit them.
Formal publication of an 1884 speech on Blood Atonement by Charles Penrose.