[dragonwriter]

There are all kinds of complexity metrics that exist that you could use to quantify the complexity of the code at issue, and for many of those metrics there are also commonly-cited standards for levels of complexity that are sources of concern.

But its still, ultimately, a matter of opinion that the particular measure and standard are really too complex for the purpose the particular code is serving in the particular project, so while you can get some facts, the relevant bit still boils down to a matter of opinion.

OTOH, the best proof that code is too complex is to demonstrate simpler code that does the same thing.