The structure of this sentence is incorrect,
but I'm not able to explain the reason why. 

> 
> It is against company policy to use mobile phones by any person when in control of this vehicle.
> 
> 
> 

I understand that the sign is obviously saying it's prohibited for any person to use a mobile phone, but the structure is completely wrong. It's the 'to use mobile phones by any person' part that's the issue, but could someone explain specifically why this is incorrect.