hi, ive heard that this definition comes from "Blacks Law Dictionary".
From a non statute law point of view and looking at your question from the view of natural law, everyone is equal and no human has the authority to control another human, unless they consent.
Now, looking at it from legislation law-
Article 21 of Human Rights Act states:
(3) The will of the people shall be the basis of the authority of government; this will shall be expressed in periodic and genuine elections which shall be by universal and equal suffrage and shall be held by secret vote or by equivalent free voting procedures.
So, 'the will of the people shall be the basis of the authority of government' - meaning that the people give consent to be governed.
You can google the definition of statute, and you will see the answer to be something like this:
: a law enacted by the legislative branch of a government 2 : an act of a corporation or of its founder intended as a permanent rule
So the government, or organisation, or business etc can make statute laws. The government makes statute laws. We do not live in a dictatorship, hence we give consent to be governed. This makes perfect sense in the definition you are looking for, in that a statute law is “A legislative rule of society given the force of law by the consent of the governed”
If it were not, then we would be living in a dictatorship.
We are also policed by consent as you are able to see from this amusing video.
if you dont want to watch all the video, then FF to 7:20 - 7:40 and you will see the police INSPECTOR state that "we are policed by consent" and that "we are policed by consent because the public want us to do it"