Well, you can argue about the value of rules, laws and legal binding direction until the cows come home. It doesn't change the point in fact. In the USA and the UK and various other countries, the rules have been made clear as they apply to aircraft commanders through the companies operating certificate. Specifically through the operations manual, which makes it clear who may and who may not enter the flight deck "in flight" and at other specific times.
There is no exemption for footballers, Bank executives, or ministers of the crown, unless they also happen to be a qualified and authorized member of the crew.
The captain and everyone under his/her command is charged with ensuring that the rules and the regulations that they operate within, are complied with to the best of their ability. There are inevitably times when compliance is not desirable or possible for reasons of overriding necessity, however entertaining the "rich and famous," or indeed anybody else, isn't one of them.
Whatever my opinion of some of these rules, I am paid and expected to ensure full compliance. If I need to deviate from that compliance, then the company and the regulator have a right to an explanation for that action. Common sense would dictate that situations do arise to reasonably justify such deviance. However you would need to come up with something good to defend this type of deviance outside of an emergency.
There are lots of rules we all love and hate. I cannot understand why I am restricted to 70 MPH on a deserted motorway at 3am in the morning. If I chose to deviate from that regulation because I feel it is absurd, that is my choice. I doubt my opinion would provide much defence to a subsequent prosecution. However if I am being paid by an employer to drive his car, I not only run the risk of prosecution, but also of breaching the likely terms and conditions of my employment.
All talk of "the captain is king" and "nazi war trials" and "maverick personality types" is all very interesting, but the rules are not optional. The truth is, most people know that.