I’m sure the definition of community property was spelled out for anyone who bought there in the vast array of documents presented at closing. That someone is prevented from displaying the flag is pretty disturbing. Nonetheless - the error is in the headline referring to “his yard”. Evidently, like a lot of condominiums - there is no land area that goes, in fee simple, along with the unit. So it’s not “his yard”.
If he doesn’t actually own the yard, then you’re right. I assumed it was his property.