“Why should American constitutional law in the 21st century depend on what English law from the 1300s?”
The reason is fairly simple to understand. If the words in the Constitution are to mean anything at all, then they must be at least they must be tied to the spirit and context in which they were originally used. This is true, whether you believe in a very restricted “original” interpretation of the meaning of the words in the Constitution or whether you believe in an interpretation of the meaning of the words that allows their meaning to evolve in the context of their “contemporary” legal meaning.
The specific requirements for eligibility for the US Presidency don’t simply demand that a person be a citizen, they specifically require a person to be a “natural born” citizen. The meaning of this common law term dates back to English common law and it is evident that the meaning of the term, as is amply evidenced in virtually all English Common Law as well as in the letters and discussions surrounding the writing of the US Constitution indicate that “natural born” refers specifically to the jurisdiction and sovereignty of the territory where a child is born and not to that of where his parent or parents were born.
There has been much talk about this being an “unsettled” matter of law. However, this is not true, since the US Supreme Court did rule specifically on the question of “natural born” in a case US vs Ark 1898 and specifically researched the meaning of “natural born” in the context of Common law to establish its meaning. After much reference to the meaning of the term in both English Common Law and with respect to its legal meaning at the time the Constitution was written, the Court ruled that “natural born” meant precisely that a person is considered “natural born”, if and only if, they were born within the sovereign territory of the United States. In fact, this is precisely why Mr. Ark won his case, even though both of his parents were Chinese and not Americans. Mr. Ark was born in San Francisco.
It should be noted that in US vs Ark, both the majority and minority opinions came to the same conclusion that “natural born” means specifically that a person is born within the jurisdiction or sovereignty of the United States. It is clear that had Mr. Ark not been born within the jurisdiction of the United States he would have lost his case and would have been deported as the US was trying to do.
It is further worth noting that the Court in US vs Ark also made specifically clear that the US could not simply pass a law, at that time the Chinese Exclusion Act, and use it to alter the meaning of “natural born”. They specifically referenced the fact that since that term was used in the Constitution, its meaning could not be altered by statute alone but would require a Constitutional amendment. The Court ruled that no law can amend the Constitution of the United States and any law that the government may attempt to use to do so is unconstitutional in its application. Congress has the power to naturalize, but it does not have the power to amend the meaning of the constitution via statute.
Legally, since the ruling in US vs Ark remains precedence, Mr. Cruz is ineligible to hold the office of the Presidency because he was born in Calgary, Canada as his Canadian birth certificate clearly demonstrates. He remains in ineligible under US law, at least until he gets a constitutional amendment passed permitting him to do so or he can provide proof that US State Department specifically claimed US jurisdiction over his birth. So far Mr. Cruz has not provided that critical piece of evidence.
The present court may attempt to reverse the precedent. However, to do so it will clearly have to waive the original meaning of the term in the Constitution, previous Supreme Court precedent, and more than 500 years of Common Law to do it.