[Wesley221]

pawn Код:

public OnPlayerStateChange(playerid, newstate, oldstate)
{
    if( newstate == PLAYER_STATE_DRIVER )
    {
        if( /* to check if the player ISNT alowed */ )
        {
            RemovePlayerFromVehicle( playerid );
            SendClientMessage( playerid, -1, "You are not allowed to enter this vehicle. " );
        }
        else
        {
            SendClientMessage( playerid, -1, "Welcome to the vehicle!" );
        }
    }
    return 1;
}

That will do the trick. Just change the if statement