I wonder if a restaurant can block police, EMT or any other type of person into their establishment. If they can block a person execising their constitutional RIGHT to enter their establishment, what prevents them, or any other business from blocking anybody else the business deems marginal?
No such right exists.
Nobody has a right to enter another's private property, even if it's a business. The business owner should have complete control over who may or may not enter. Of course, legislation has infringed on that authority over the years. (CRA, ADA, etc.)
A LEO has the power to enter private property over the owner's objections, under specific circumstances, because of limited and specific authority granted him by law, but not because he has the right to.