Following his departure from the U.S. Treasury Department, Brian Nelson has emerged as a prominent voice in the crypto sphere, now working on Vice President Kamala Harris' presidential campaign. Prior to this, Nelson had already made a significant impact in the crypto space during his tenure as the Treasury's undersecretary for terrorism and financial intelligence.

He led the charge against digital asset mixing services, highlighting their potential connections to terrorist organizations and illicit activities, and sought to expand the federal government's oversight of the sector. Nelson's primary concern was the potential for crypto to be exploited by malicious actors, including international terrorists and crime cartels, who could utilize anonymizing services like Tornado Cash to launder funds undetected.

To counter this, Nelson worked to leverage government resources to curb the misuse of this technology. After spearheading the effort to impose sanctions on Tornado Cash in 2022, Nelson became a key figure in the federal government's efforts to regulate the crypto industry.

Under his guidance, the Treasury Department adopted a more antagonistic stance towards the sector, going beyond the measures proposed by the Internal Revenue Service to establish tax standards that could impact decentralized finance (DeFi). Nelson oversaw an initiative by the department's financial crimes unit to classify mixing services as a 'primary money laundering concern,' emphasizing his goal of promoting transparency rather than outright banning these services. However, a recent federal appeals court ruling has dealt a significant blow to Nelson's legacy, determining that the Treasury Department overstepped its bounds in targeting the software underlying Tornado Cash transactions. Moreover, the government's anticipated shift towards a more open approach to digital assets in 2025 may further overshadow Nelson's crusade against the illicit financing aspects of the crypto space.

This profile is part of CoinDesk's Most Influential 2024 series, featuring this year's nominees.