A federal judge in Massachusetts has ruled that DOMA (Defense of Marriage Act) is unconstitutional. Chris Hayes anchored Rachel Maddow's show and led off with this segment and interview with Martha Coakley.

We begin tonight with breaking news out of Massachusetts. A federal judge ruled that the federal government's ban on same-sex marriage is unconstitutional. U.S. District Court Judge Joseph Tauro decided that the defense of marriage act violates the fundamental principles of this nation.

With that, the judge made advocates of marriage equality very happy. One of the rulings involved seven couples and three widowers, all of whom who had been ineligible for the federal benefits that come with being lawfully wed thanks to the 1996 Defense of Marriage Act. That law required the federal government to ignore for federal purposes any marriage not between a man and women.

Same-sex wedded couples have no access to family health insurance, no social security survivor benefits, no joint filing of federal taxes.

There are two salient things about the ruling. The judge granted the plaintiffs what's known as summary judgment. Both sides filed their arguments and the judge decided he didn't need to hear another word.

The remarkable part of the ruling is the reason for it. In addition to ruling that DOMA violated the equal protection clause, he also invoked the Tenth Amendment, which Chris Hayes points out as the "holy grail" of conservative thought:

Judge Tauro saying the rationale strains credulity. Judge Tauro ruled that a key part of the bill violated a couple's right to equal protection. Judge Tauro also ruled for the Commonwealth of Massachusetts, saying the federal government wrongly forced it to discriminate, writing "the federal government, by enforcing DOMA encroaches on the province of the state and offends the Tenth Amendment.

The tenth amendment is the "don't tread on me" amendment. It's the one conservatives are using to repeal health reform. It's Texas governor Rick Perry's favorite battle cry. Now, today, the Tenth Amendment means gay couples are one step closer to being treated equally in this country. Don't tread on them either.

I believe the Obama administration concurred with the judge's ruling, which is why the President issued his executive order protecting the rights of gay couples with regard to health care and ordered benefits extended to same-sex partners.

It does, however, place the DOJ in a weird position. Since the DOJ is responsible for enforcing the laws on the books, they're going to have to appeal this judge's ruling, even if the opinion inside the administration is that the judge was right. This is their duty under the law, and it carries the risk that this case will go to the Supreme Court for a final resolution. When it's appealed, don't assume the administration is against the ruling simply because DOJ is doing its job.

If it reaches the Supreme Court and Elena Kagan is confirmed, it affirms the wisdom of her refusal to answer the question about DOMA's constitutionality. Had she answered that question, she would have had to recuse herself from any proceedings that related to it, which would have left an unbalanced court to decide the case.

In any event, this is a landmark decision which sets a much faster pace for the eventual repeal of DOMA.