If someone is travelling from country X through country Y with documents destined for country Z, and the government of X wants the documents to reach Z unobserved, this is the usual use-case for a government-of-X diplomatic pouch. (Or, if it’s the Z embassy sending to Z, a government-of-Z diplomatic pouch.)

I wonder if you could make the case here that the US government should be ensuring the functioning of its judicial system by issuing lawyers who leave the country a “loopback” diplomatic pouch—one issued by X, destined for X, protected during travels to all not-X.

(This could currently be achieved by X-gov issuing a pouch destined for X-embassy in transit country Y, which the traveller must visit to have their documents re-wrapped in a pouch from X-embassy back to X-gov. The change would just simplify things by making the visit to X-embassy unnecessary.)