Oh, really? Is it up to the states to decide if the law of gravity exists, too? A fetus is a life that arises from human reproduction and if left alone will become a little boy or girl. To say that it is not a person is on the order of saying that thunder is the sound of God bowling.
But, OK, let's go with your legal angle. The state where you live decides that bipeds who have screen names beginning with the letter L are not humans and therefore have no protection under the 14th Amendment. They issue permits allowing people to hunt them and get a $500 bounty. You'd be OK with that, it would be perfectly legal?
Oh, and one other thing, if it's up to the states to determine whether a fetus is, in fact, a person, why isn't it up to the states to decide if owning an African is really an example of involuntary servitude? If a judge decides that bipeds browner than a certain shade are not really humans and selling them as cottonpicking machines is therefore not slavery, who is the SCOTUS to say that's wrong?