It is murky, but he is an american citizen. What is truly murky is birthrite citizenship. If an american couple have a child while traveling in China, the child is not automatically a Chinese citizen, he or she is a. American citizen. Reverse the couple, Chinese citizens have a baby in the us, the child is american.

Since Cruz is a citizen, it would be highly unlikely his citizenship would be revoked. Laws can't be ex post facto but a ruling by the courts could change it for future generations. As for Cruz, the argument is moot. He is currently a citizen and that ain't gonna change, sorry.