It's North Korea talk because they are the extreme example of illegitimacy.

"A sovereign state"

Sovereign by who's terms?

A gang of people hold another group of people hostage, we have to respect their supposed sovereignty?

And the sovereignty of the majority of the people who reject the regime and who are murdered, tortured?

We're just going to respect a group of thugs claim to control national sovereignty?

The point being - the regimes lack of legitimacy aggravates their claim to 'sovereignty'.

"They have every right to resist this criminal assault."

They probably don't (lack of legitimacy) - and - this really isn't a situation of 'rights' anyhow, this is a break down in order, it's just about power.

And of course - 'rights' - the rights of their citizens murdered and tortured, how do that integrate into this question?

There are international laws here, but there is also legitimacy.

If we could be certain (and we almost could) that literally the vast majority of people in Iran, do not believe in the legitimacy of their own government ...

... then it's ridiculous to talk about 'a sovereign state' or 'a leader' has been killed.

There is a 'Theocratic Feudal Clan' holding power in the country, and they were attacked.

Israel is a very odd state, but with similar lack of legitimacy - except that Iran has made directly claims to the total destruction of the state, and Israel's internal crimes notwithstanding, they have a practical right to defend themselves.

The assault was ordered by a semi-Feudal Lord of 'House Trump' - as US citizens don't support this war, neither was the Executive given consent by Congress.

'Sovereignty' is mostly rhetorical term in a context were legitimacy is not applied.

This is a war being fought where none of the citizens approve of any of it, the claims on all sides are aggrandized.

This conflict is probably best understood like those in Europe before Napoleon and national armies etc..