It doesn't say he has a blank check. It says he has a $700,000,000,000 check very specifically. The rest says the Secretary is the final decision maker regarding the matters that the Secretary is given under the law. My assumption is that there may be laws on the books specifically prohibiting the Secretary from taking these actions under normal circumstances. That section just says in the limited circumstances described in the law, the Secretary's actions are legal.
Regarding your headline, it's easy to make the argument that once you allow people to form corporations to limit their liability, the market is no longer truly "free" anymore. Certainly not equitable at the very least.
Christopher S. Penn It's blank in the sense that it's not a fixed $700B. It's a debt ceiling, so he can buy as much as he wants as long as some of it gets sold off to stay under the $700B ceiling.