From what I read it is not a states right argument but an argument that the supreme court is supposed to interpert the laws not make them. Some quotes:

"Today, however, the Court takes the extraordinary stepof ordering every State to license and recognize same-sexmarriage. Many people will rejoice at this decision, and I begrudge none their celebration. But for those who believe in a government of laws, not of men, the majority’s approach is deeply disheartening. Supporters of same-sexmarriage have achieved considerable success persuading their fellow citizens—through the democratic process—toadopt their view. That ends today. Five lawyers have closed the debate and enacted their own vision of marriageas a matter of constitutional law. Stealing this issue from the people will for many cast a cloud over same-sex marriage, making a dramatic social change that much moredifficult to accept."

"But this Court is not a legislature. Whether same-sex marriage is a good idea should be of no concern to us.Under the Constitution, judges have power to say whatthe law is, not what it should be. The people who ratifiedthe Constitution authorized courts to exercise “neither force nor will but merely judgment.” The Federalist No. 78, p. 465 (C. Rossiter ed. 1961) (A. Hamilton) (capitalization altered)."

Yep. Maybe we differ in our understanding of the phrase "states' rights argument" but the very first sentence you quoted screams "states' rights" to me - "Today, however, the Court takes the extraordinary step of ordering every State to license and recognize same-sex marriage."

The SCOTUS didn't make any law here, they simply said the laws being passed were unconstitutional. Isn't that what they're supposed to do?

I think the "making law" thing is reference to creating novel kinds of unconstitutionality that often contradict older notions.

Not sure why you got downvoted because I'm reading Roberts' decision now and that's a big part of it.

Well all rights not defined in the Constitution are inherently in the domain of the states. Marriage is not within the Constitution and this was not a Constitutional issue. This came before the courts mainly because Federal Law needed to be applied to all states for issues concerning pay, benefits, visitation, and so on. So it was more similar to interstate commerce than anything, it certainly wasn't under the equal protection clause because there had not been a national law denoting the designation as existing. No any attempts to say other wise can be slapped down by 14th Amendment challenges - as in gay couples are designated properly within the confines of the law (likely it may take a bill similar to the civil rights law to make it unquestionable)