The word 'governed' probably has the wrong connotations.  Perhaps it is better to say that the "evolution of the network is decided by the code people freely choose to run."

Arguably, it is impossible to know with certainty what the current consensus rules are, other than by creating blocks and seeing if those blocks are accepted into the longest chain.  We can't know for sure what code the economic majority is running--we could ask them or they could tell us--but they could lie.  Proof-of-work is where we "put our money where our mouth is," as it were.