> Any country can reject non-citizen entry, for any reason or no reason at all. […] This necessarily includes border controls, which any country can decide to make as onerous as they please.

Or, a country could set rules that specify what they will and won't do as part of their entry controls. Just because it's a kind of an "absolute" power doesn't mean you can't still self-impose rules. The benefit being attracting more leisure and business travellers.