I am always amazed by these "no-regulation" arguers - how are you doing to resolve disputes?

Suppose I want to sell my product, and find a company willing to buy, a middle manager signs the contract. When the company recieved my product, it refuses to pay, says this person was not authorised to sign the contract on behalf of the company.

Must the company prove the purchase was unauthorised, or must I prove the employee was authorised? Suppose employee was unauthorised, is it my or the company's problem if this guy 'took initiative', who eats the loss?

What if they already used my product and only realised after the bill came due? What if the deal was overpriced like 10x from market average? What if the guy's title says 'Head of procurement' but the company swears their bylaws don't allow him to authorise purchases?

They weren't talking about the concept of regulation. Just the reality of the US's ones.

And I think you're talking about contract law, not regulations.