For all the people commenting, the ITAR rules still apply for TLS, if you want to use TLS in an app for iOS/Android, one of the requirements is to get an ITAR exemption as part of the app review [1].

The US sanctions are imposed on entire nations (eg Iran), so LetsEncrypt have no option but to state in their conditions that their service is not available. They don't have a choice as a US organization operating under US law.

Whether they choose to enforce that through technical means (eg blocking IPs etc) is up to them.

[1] https://developer.apple.com/documentation/security/complying...