I feel like Iran and Venezuela are bad examples as they are typically denied access to much of the global financial system. It’s normally pretty easy to move gold around and this process is handled by banks. Of course you might not get the same gold bars if you move gold between countries (for one thing they tend to come in different sizes in different places) and it likely won’t even be physically the same gold, but the banks tend to handle the arbitrage of taking physical gold to refineries across to move it from one market to another (though there were some worries this might break down between the US futures markets and London physical markets due to coronavirus restrictions)