"We are firmly convinced the exclusion of gay and lesbian people from the institution of civil marriage does not substantially further any important governmental objective," the Supreme Court wrote in its decision. "The Legislature has excluded a historically disfavored class of persons from a supremely important civil institution without a constitutionally sufficient justification."
This is huge, bigger than Tinker, probably as big as Griswold v. Connecticut. It's a state ruling, but having read Bobby Hanson's original ruling, is very easy to apply at a federal level. The ruling deals with equal protection under state rules, but the decision also went into detail on applicable federal rules because of rulings that apply to states (like Griswold).
Things just got VERY interesting. Federal unconstitutionality overrules state constitutions, period. Hanson's breakdown presents a clear argument that barring gay marriage is unconstitutional under the US Constitution which means those state constitutional amendments barring gay marriage could easily be voided. Expect this one to go up the ladder quickly because of this. Someone in a state that has such an amendment will challenge the state rule in federal court, using the Iowa decision, depending on how things go with the California Supreme Court and Prop 8, I would expect it challenged there in the 9th Circuit, but there are other possibilities, Wisconsin and Florida are other likely locations for challenges.
Finally, there is no, none, zero chance of a federal ban amendment getting though anything resembling the current system. Doing so would require a 2/3 vote of both houses, followed by ratification of 2/3 of the states. Right now it can't even make cloture in the Senate, is even farther from super-majority status, and then would need approval in 2/3 of the states? There is no part of that process it would currently pass, or would have at any time in the last 20 years.
Iowa high court legalizes gay marriage in state