3. Avoid Two-Way Engagement
Reviewing an unsolicited patch from a contributor in a sanctioned region should generally be fine, but actively engaging them to better understand their issue, diagnose the problem, or help improve a patch or modify code would likely cross the line. If the contributor is linked to a sanctioned entity or region, in general, it is best to keep communications strictly one-way. If a patch is received and you improve it and submit it upstream, that should be fine, but going back and forth in communications with the SDN developer likely would not.
https://www.linuxfoundation.org/blog/navigating-global-regul...
Long story short, it’s because of sanctions.