Monero transactions use ring signatures and are very difficult to trace. Each transaction is signed by at least 11 keys and there's no way to tell which key is the source of the coins. The source and destination addresses as well as the transaction amounts don't show up on the block chain. Even if they did people can just make new subaddresses to make correlation extremely difficult if not impossible.
The US treasury tried to sanction a Monero address once. They ended up sanctioning a transaction identifier.
https://www.treasury.gov/ofac/downloads/sdnlist.txt
> Digital Currency Address - XMR 5be5543ff73456ab9f2d207887e2af87322c651ea1a873c5b25b7ffae456c320;
Note the lack of a 0x prefix. Here's the transaction on a block explorer:
https://localmonero.co/blocks/search/5be5543ff73456ab9f2d207...
