Here is the paragraph Let's Encrypt added to their Subscription Agreement on 2026-06-04:

You are not a person or entity that is:
(a) located in, organized under the laws of, or ordinarily resident in any country or territory that is the target of comprehensive U.S. sanctions;
(b) a prohibited or restricted party under U.S. or other applicable sanctions and export control laws and regulations;
or (c) owned or controlled by or acting on behalf of anyone described in (a) or (b).
You agree to use Let’s Encrypt Certificates and any services provided by or on behalf of ISRG in compliance with applicable U.S. export control and sanctions laws and regulations.