On February 26, 2018, the Republic of the Marshall Islands passed the Declaration and Issuance of the Sovereign Currency Act. This would create a new cryptocurrency, called the Sovereign, to be used along side the US Dollar in the Marshall Islands as legal tender for all debts and exchanges in the country. The idea is to have their own currency independent of the US Dollar without the overhead of a mint, etc. The intent is to offer an Initial Coin Offering later this year and begin circulation.
However, the International Monetary Fund has given the Marshall Islands a warning against adopting the coin. They offer a lot of reasons not to, but the real reason, as far as I can tell, is that the sole bank in the Marshall Islands has a relationship with an American bank stateside. This American bank apparently is really unhappy about the issuance and may break off the relationship as a result. This would be very bad for the Marshall Islands.
There are some legitimate concerns about switching a nation, especially one so small and vulnerable to monetary shifts over to a cryptocurrency due their volatility. After all, the Marshall Islands are not solely adopting the Sovereign, they are keeping the fiat US Dollar. If the experiment doesn't work, they still have the Mighty Dollar.
However, the IMF warning as presented in the BBC article sounds a lot like a threat rather than a warning. As phrased, the IMF warning comes across rather more "Nice island you have there. Pity if something bad were to happen to it." rather than "You need to be very careful about how you do this."