I go along with what Dave says, why give palyers any kind of ammo they could use against yo?
Also, in terms of sponsorship, we have a slightly different set-up here in NZ. Every referee, from ASB Premiership down to local senior level is sponsored by the same company - ASB. So, our black, and yellow shirts all have the ASB logo on the sleeve.
However, over summer I play in a social 5-a-side league, and when we were a ref short, I threw on the yellow jersey and reffed a game. Boy, did I get a talking to for that!
Quite simply, the shirts with the NZF and ASB logo are only to be worn in NZF competition. I have a different set of shirts for the social/junior games.Same colours, but without the sponsor logo.
It is quite possible for anybody to buy the shirts, over the counter, with the NZF badge on, but impossible to get them with the sponsor logo unless you are given it by your Federation.