25.8% of the validated blocks in Ethereum are rejected under the US Office of Foreign Assets Control (OFAC) regulations. This means that they do not process transactions on the network that have been reversed under the current laws of that country.
Specifically, the transactions that are subject to this oversight are those of the validators who use them relays (Software for managing and transferring transactions) with MEV-Boost. These relays Will not include transactions that interact with sanctioned addresses or protocolsTornado Cash transaction mixer, for example.
According to mevwatch, 1 in 4 blocks are validated on the network after merging Fall into this group, those who use relays Flashbots and BIoXroute Structured, Blocknative, and Eden. Those not regulated by OFAC are BIoXroute Max Profit and BIoXroute Ethical and Manifold.
It is necessary to clarify that the fact that the auditor complies with OFAC regulations does not mean that the Ethereum transaction is completely ignored. It can be taken by another validator and this will not affect its registration in the network.
also, This is a condition that only affects new transactions. Of course, no validator can change previous transactions (which have already been approved), due to the immutability of the network.
What is MEV-Boost?
MEV-Boost is an open source software that allows dealers to Ethereum sells space in blocks that validatesomething that has been happening to a large extent in this network since the merger was achieved and the mining was abandoned with proof of work (PoW). With MEV-Boost, validators can increase their bonus up to 60%.
This is an idea developed by Flashbots, a group of developers who disagree with implementing MEV (Maximum Extractable Value), a technology to reorganize transactions to make the most of the commissions paid by Ethereum users.

What about the rest of the blocks in Ethereum?
Aside from the 25% of blocks using MEV-Boost that OFAC rejects, there are Another 4% also use this software, but they are not subject to regulations Americans. Finally, the remaining 70% of blocks are validated without resorting to this tool.
OFAC is a United States government entity administered by the Department of the Treasury. This body has shown an interest in regulating certain operations in the cryptocurrency world in the recent past.
As reported by CriptoNoticias in August, the Treasury Department Prohibited interactions with the Tornado Cash transaction mixer protocoland even the Dutch authorities arrested one of its developers.
By this measure, the United States Ethereum users left without an important privacy tool Arguing that this program facilitated money laundering. However, after a short time, it was revealed that this is not the case in most cases.