It isn't. Everyone who has tried has failed.

CipherTrace's method for tracing Monero transactions was to combine a whole bunch of off chain data, such as people publicly posting their addresses or transactions, data from centralized exchanges and other third parties, social media profiles, and so on. They did not manage to do anything on chain. The IRS offered a $1.25 bounty to anyone who could trace Monero transactions. CipherTrace were unable to claim it.

After going unclaimed for over a year, the IRS instead gave $500k each to Chainalysis and Integra to work on Monero tracing tools, with the prize of a payout if they could build anything useful. No prize payout has been made.

Note that no other "privacy" coin has ever had such a bounty, because they can all already be easily and widely traced by a whole variety of blockchain analysis firms.