The "executive branch" was the king. The point is, you have to be judged by the law, rather than the will of any official.
The king was not just the executive, as there was no separation of powers. All legislative, executive, and judicial power was ultimately held by the Crown.
I would agree that, in practice, the executive branch is the only one that actually "takes away" life, liberty, or property. However, the legislature may, for instance, attempt to do so by enacting a law.
For the legislature to prohibit cohabitation, and for the executive to enforce such a law, deprives individuals of the liberty to live where and with whom they please. This deprivation of liberty is entirely arbitrary, and is unconstitutional.