Codes only work through US and Canadian IPs. They block the use of proxy servers in the US so yes, Destiny in a way is a US pay to gain/win. If you reach lvl 40 by codes in US, they will have an advantage on the rest of the world who lvl by playing in the next IB for example. But, Bungie/Activision seems to aim to alienate players outside the US. Time will tell if they can live on US player base only. Next DLC will be 100$ to cover the loss of players abroad...