[spywaregorilla]

The key term here is "apparent authority". You don't need to be granted authority for each and every thing you do, but if you start grossly doing things you were not supposed to do, that's mostly just fraud on your end.

The common example in textbooks is someone continuing to do business as an employee after having been fired. They can still make valid deals with other entities due to apparent authority if they're not clearly made out to be separated.