To begin with, check the terms of the relevant employees' contracts of employment. If the contracts are silent on this - if they say nothing about it - then in theory at least your sales force might be able to argue that you are breaching terms established by custom, even if never spelt out. If in doubt, consult a lawyer about the situation, with a view to ensuring that your terms and conditions make it quite plain in future that the choice of company car is yours.
