If the state has ultimate authority and power over society, then it can guarantee anything it likes. The individual or group ownership over the means of production is guaranteed by the state in most Western countries. Not in any 'ultimate' sense which superceeds the state's authority (yes, that would be absurd), but in the prosaic sense of every day normal expectations it does. You can test this idea of guarantee out for yourself by trying to rob a business, for example.
At any rate, you may be misinterpreting my original comment, which was a response to the question:"Was the economy of the USSR "state capitalist"?"
Capitalism, as a type of economic relationship, was incubated within the state. There has never been capitalism without a state. So the term 'State Capitalism" is not only redundant, but kind of an oxymoron, at least strictly speaking. That was my point. In the West, the state keeps a more or less 'hands off' approach towards ownership and profits (as well as prices and wages). The state still heavily regulates and subsidizes industry, however, because otherwise no regulations would simply destroy a country, and along with it the state.
In the USSR, all industries (with more than 5 employees) were ultimately under the ownership and control of the Soviet Government. Farms were collectized and nationalized, and prices and wages for everything were set by the government. In addition, production output levels were also determined by the government. The degree and the kind of state controls became less under the reforms of Gorbachev.
I'm not sure if you're implying this means that therefore the Soviet government was the 'real' or 'only' capitalist, for this would be to misunderstand the nature of capitalism. Capitalism doesn't mean the mere existence and use of money or assets (i.e. capital) for exchange. It means the private ownership of the means of production, and usually includes the right to keep the profits of production. That's how most people use the word. We call nation states that allow this kind of ownership "capitalist", and those nation states that do not, "socialist" or "communist" (these terms are also highly misleading). State (i.e. public) control or ownership of the means of production is therefore, by definition, not private, and thus not capitalist.
The notion of a distinction between personal/private commercial activity and state activity (even state commercial activity) is inherent to the usage of the concept of capitalism. It can be tempting to think of a state like the former Soviet Union as one big society-wide corporation, however, capitalism is a little more complicated than that.