If you withdraw your funds from a CEX to any wallet, I think the CEX will mark it as sent to you, and would probably testify that, as far as their records can tell, you still have it. I would not be surprised if a judge said that's enough data to conclude you *do* still have it. If you claimed to sell, spend, or lose all of it, I would not be surprised if a judge said that's an unlikely story and consequently "innocent until proven guilty" doesn't apply. If that happened you might need to show evidence to probe your case, and might be considered to at least own whatever amount you can't show convincing evidence of selling/spending/losing. If you used a standard bolt11 invoice to withdraw the funds, they would have full route info from themselves to your LN wallet and could trace the funds that far. You could use tools like lnproxy.org to throw them off, but they might subpoena or purchase your "real" routing info info from lnproxy.org or whatever competitor(s) you use. If your wallet is connected to a routing node like Amboss or Phoenix, and you're not using tor, those guys have your IP address and can also see when you close your channel and send your funds to cold storage. They might act as informants against you if their routing nodes showed up as the "last hop" on the path from the CEX to you. All that said, I don't think they would be unable to *deterministically* trace the funds if you use tor + route blinding (e.g. through lnproxy plus a few of their competitors, or bolt12) but they probably don't need to -- if they are confident you withdrew the money *somewhere* then you will be marked in their books as having whatever amount of money you withdrew, regardless of where you sent it afterwards.

In he last paragraph there was an important typo. I wrote "I don't think they would be unable..." but it should say "I don't think they would be able..." I used the "Edit" feature in amethyst to fix it but just in case your client doesn't show edits, I'm clarifying here as well.