"Surely for your lifeblood I will demand a reckoning; from the hand of every beast I will require it, and from the hand of man. From the hand of every man’s brother I will require the life of man.
“Whoever sheds man’s blood,
By man his blood shall be shed;
For in the image of God
He made man."
This is not part of the Mosaic law. This command was given to Noah, and is not isolated to the children of Israel. It's a direct command from God for the good of the people, and which survives the dispersion of the children of Israel.
https://www.biblegateway.com/passage/?search=Genesis+9&version=NKJV