DETROIT (Reuters) - Michigan's ban on same-sex marriage violates the U.S. Constitution and must be overturned, a federal judge ruled on Friday in the latest in a series of court decisions to allow gay couples to marry.

Michigan Attorney General Bill Schuette said he sought an emergency stay and appeal of the ruling.

(Reporting by David Bailey in Minneapolis and Bernie Woodall in Detroit; Editing by Cynthia Johnston)

Update: The decision can be read in full here.

Some key quotes from the ruling:

District Judge Bernard A. Friedman didn't think much of the state's star witness, University of Texas sociology professor Mark Regnerus...

"The Court finds [Mark] Regnerus's testimony entirely unbelievable and not worthy of serious consideration. The evidence adduced at trial demonstrated that his 2012 'study' was hastily concocted at the behest of a third-party funder, which found it 'essential that the necessary data be gathered to settle the question in the forum of public debate about what kinds of family arrangement are best for society' and which 'was confident that the traditional understanding of marriage will be vindicated by this study.'...While Regnerus maintained that the funding source did not affect his impartiality as a researcher, the Court finds this testimony unbelievable. The funder clearlyl wanted a certain result, and Regnerus obliged."

The judge also didn't buy the state's position that children raised in a same-sex marriage had a tougher time and fewer educational opportunities. But even if that was the case, how could the state really limit marriages only to people with optimal situations?

"Taking the state defendants' position to its logical conclusion, the empirical evidence at hand should require that only rich, educated, suburban-dwelling, married Asians may marry, to the exclusion of all other heterosexual couples. Obviously the state has not adopted this policy and with good reason. The absurdity of such a requirement is self-evident. Optimal academic outcomes for children cannot logically dictate which groups may marry."

-- "Many Michigan residents have religious convictions whose principles govern the conduct of their daily lives and inform their own viewpoints about marriage. Nonetheless, these views cannot strip other citizens of the guarantees of equal protection under the law."

-- "Further, the Court rejects the contention that Michigan's traditional definition of marriage possesses a heightened air of legitimacy because it was approved by voter referendum. The popular origin of the [marriage ban] does nothing to insulate the provision from constitutional scrutiny."

-- "In attempting to define this case as a challenge to 'the will of the people,' state defendants lost sight of what this case is truly about: people."

[Image via Agence France-Presse]