Strictly speaking, I believe he is right. US constitution does not say anything about abortion. Obviously, I think that Roe vs Wade was the right decision, but that was taken by a bunch of unelected judges because the US political system has made it impossible for the senate/house to legislate. From what he says though, he looks more to want to overrule it cause he doesn't like abortion too much. While Scalia for example (at least on what he said), wanted to overrule it cause it had nothing to do with the constitution, not because he was personally against abortion. Either way, Thomas is a twat.
In most countries I am aware of, abortion was legalized by the senate passing a law (or in the case of Ireland, a referendum taking place).