Hard to regulate. A lot of the retatrutide sold today is marketed on Discord & Telegram groups and paid for with crypto. It is infeasible for customs to open every last package entering the US, so this avenue will continue to work. The only gov't that could realistically stop it (for a while at least) is the Chinese. And they do, occasionally, shut down a manufacturer for a while. Though not because they are shipping GLP1s to the states.