I reckon the G20 nations can never fully enforce any regulations forced on the cryptospace.
However, it also stengthens the rationalization to use fungible and anonymous cryptocoins like Monero and Aeon. If those Iranian ransomware facilitators knew of and used a strong anonymous coin, they would never have problems in moving them or trading to fiat or bitcoin.
In relation to cryptocurrencies or “crypto-assets” as they are referred to in the document, the G20 has agreed to a regulatory approach in line with FATF standards. Section 25 of the official declaration reads:
"We will regulate crypto-assets for anti-money laundering and countering the financing of terrorism in line with FATF standards and we will consider other responses as needed."
In addition, the countries will work together and monitor the digitization of the global economy that’s happening at a rapid pace. An excerpt from section 26 reads:
"We will continue to work together to seek a consensus-based solution to address the impacts of the digitization of the economy on the international tax system with an update in 2019 and a final report in 2020."
Bitcoinist reported last week that the U.S. has taken the first-ever action against two Iranian ransomware “facilitators.” The U.S. Treasury’s Office of Foreign Assets Control (OFAC) published two Bitcoin wallet addresses warning the cryptocurrency and financial communities that anyone transacting with the accused could be subject to secondary sanctions.
However, it still doubtful that these measures will be successful in preventing Bitcoin and cryptocurrency transactions at the protocol level. In fact, Bitcoin was intentionally designed to be censorship resistant, borderless and politically nuetral form of money.Read in full https://bitcoinist.com/g20-regulate-cryptocurrencies-fatf/