This is the flag of the Houthis [1], they are sponsored by Iran, as are the likes of Hezbollah, and Hamas. They have similar language in their charters.
How is that not casus belli?
1 - https://en.wikipedia.org/wiki/Sarkha
US first started bombing Yemen in 2002. That flag was adopted by Yemen in 2014
Why would that be any casus belli?
US first started bombing Yemen in 2002. That flag was adopted by Yemen in 2014