According to Justice Scalia's comments in the video below, "Natural Law" is whatever the majority says it is. So, if the majority decides that same sex marriage (for example) is not to be allowed, then that is what "nature" dictates. It follows, then, that if the majority votes that public corporations should not have the same free speech rights as natural persons, then that should be law, despite constitutional protection (as interpreted by the Supreme Court). In reading Justice Scalia's comments during oral arguments and his decisions, one would conclude that Justice Scalia fancies himself an historian. How many times in the course of American history has "natural law" been used to justify denial of basic rights to unpopular minorities? In a democracy, is there not a need for an institution that protects against the tyranny of the majority?
Justice Scalia also queries what qualities of judges make them more qualified to determine what the law is than the democratic majority. This video can be a good device to raise the counter-majoritarion difficulty for class.