It depends what you call a rule. There is a very wide body of secondary rules, mainly to do with eyes. E.g. a group with two point eyes is alive. A row of 4 empty points where all boundary stones are a single chain is worth 2 eyes.It is a known fact that Go is more complex than chess. But why? It is because Go has fewer (and less strict) rules than chess...
If you specify more rules to the solution, it makes it more organized and it won't completely cover the problem.The above rules are exact and don't lose information. (You need to define rules that say the defender is not allowed to fill his own eyes, and not allowed to play to destroy a known 2-eye region, but you don't lose any solutions doing that.)
It is like this: it is possible to approximate higher level function with a number of low level curves, but it'll never be 100% match.
And in Go this small difference means a wrong move and a lost game.