US Treasury Prohibits Transactions With Russia's Central Bank, Wealth Fund & Finance Ministry, 28 Feb

The US Department of the Treasury's Office of Foreign Assets Control (OFAC) has prohibited United States citizens from engaging in transactions with Russia's Central Bank, its National Wealth Fund, and the Ministry of Finance.

This action effectively immobilizes any assets of the Central Bank of the Russian Federation held in the United States or by U.S. persons, wherever located.
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The United States has not taken this action alone. On February 26, 2022, partners and allies committed to imposing restrictive measures that will prevent the Central Bank of the Russian Federation from deploying its international reserves in ways that would undermine the impact of United States sanctions and the European Union followed up with their restrictions last night. Our actions demonstrate global support for Ukraine and the commitment to hold Russia's threatening, authoritarian rulers responsible for their HEINOUS actions.
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Today's actions were taken pursuant to Executive Order (E.O.) 14024 [19 Apr 2021], which authorizes sanctions against Russia for its harmful foreign activities, including violating well-established principles of international law, such as respect for the sovereignty and territorial integrity of other states.
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The Russia-related Sovereign Transactions Directive will disrupt Russia's attempts to prop up its rapidly depreciating currency by restricting global supplies of the ruble and access to reserves that Russia may try to exchange to support the ruble.  

Contemporaneously with the issuance of this directive, OFAC is issuing a general license to authorize certain energy-related transactions with the Central Bank of the Russian Federation and will follow with other authorizations and guidance as needed.

Yellen added that in coordination with partners and allies, the US was "following through on key commitments to restrict Russia's access to these its own valuable resources."