[Sandbox]Code to prevent player from changing their model?

Does anyone have any idea of how i could prevent a player from changing their player model?
The gamemode is sandbox.

Complete guess I have never dealt with Sandbox, worst case scenario consider it a bump. Maybe blocking “cl_playerskin” would do the trick. I am sure someone else could shed some light on that.

Good luck!

function GM:PlayerSetModel( ply )
   ply:SetModel( "models/player/odessa.mdl" )

Source: http://wiki.garrysmod.com/page/GM/PlayerSetModel