Non-commercial flying outside of the job is allowed as it does not decrease the block hours available to the company. The company therefore has absolutely no right to say anything about it, and therefore doesn't do it. If you want to instruct in a flying school (that is commercial, in a club it isn't) you have to get a permit for it.
In fact we are encouraged to train our basic flying skills while flying the line as well by regularly flying manual and raw data, just to keep our skills up as many of us do not fly outside of the job anymore, be it for lack of money or simply time.