It was only six months ago that Attorney General Eric Holder sent the letter to House Speaker John Boehner (R-Ohio), informing Boehner that he and President Obama had concluded that courts examining classifications based on sexual orientation should apply ”heightened scrutiny” to them.

Under such a heightened scrutiny – which the letter explained is a decision made by courts about whether, under constitutional guarantees of equal protection, a law’s classification is suspect – Holder went on to tell Boehner that the administration had determined that Section 3 of the Defense of Marriage Act was unconstitutional and that the Department of Justice would no longer defend the law in court.

Section 3, which defines ”marriage” and ”spouse” in federal law as referring only to opposite-sex marriages, was under challenge in two cases that Holder explained necessitated the decision about what level of scrutiny – rational basis, intermediate scrutiny like that applied to sex-based classifications, or strict scrutiny like that applied to race-based classifications – should be applied to sexual orientation classifications.

With some level of heightened scrutiny applied, as Obama and Holder decided was appropriate based on their analysis of several factors considered when determining the level of scrutiny to apply, the decision that DOMA’s definition of marriage was unconstitutional was relatively straightforward.

The impact of that decision in the months since, however, has been all but straightforward, finding its way into cases and considerations of all types – from bankruptcy filings to civil-rights violation investigations and from ”Don’t Ask, Don’t Tell” to immigration cases.

The letter itself made clear that its conclusion about DOMA’s constitutionality would apply to all challenges to DOMA pending in the courts – and that DOJ would give Congress the opportunity to intervene in those cases, if it so desired, to continue a defense of the 1996 law.

In addition to the two cases at issue in the letter – Edith Windsor’s challenge in New York brought by the ACLU and a lawsuit brought by the Gay & Lesbian Advocates & Defenders in Connecticut – there also quickly were three cases impacted by the decision: two cases – one brought by GLAD and the other by Massachusetts – on appeal before the U.S. Court of Appeals for the First Circuit, and a challenge brought by Karen Golinski, a federal court employee in California who is represented by Lambda Legal.

But first, the government had to defend its appeal of the case challenging the constitutionality of ”Don’t Ask, Don’t Tell.”

In Log Cabin Republicans v. United States, the government argued on Feb. 25 that the appellate court should not decide whether DADT is constitutional but should instead only look at whether the DADT repeal process itself is constitutional. Although the government has continued to argue that the military context could present different questions about the constitutionality of sexual orientation classifications like DADT, it was clear that the heightened scrutiny decision had altered the way the government could argue its appeal.

Then, on Feb. 28, DOJ filed its response to an inquiry from the judge in Golinski’s challenge, noting that the Justice Department believes that Section 3 of the Defense of Marriage Act is unconstitutional and that Golinski’s case could be impacted by that decision. Accordingly, DOJ stated that it included her case on a list of cases sent to Boehner to ”provide Congress a full and fair opportunity to participate in the litigation.”

Boehner, convening the Bipartisan Legal Advisory Group, decided to take the opportunity. The group – which consists of the speaker, majority and minority leader and majority and minority whip – voted along party lines 3-2 to authorize the House counsel to defend DOMA in litigation.

As the BLAG began its defense, other ripples of the DOMA decision began to be seen. In March, DOJ released the report of the conclusions reached by the Civil Rights Division’s investigation into the New Orleans Police Department. The report represented the first time that DOJ applied the heightened scrutiny standard in the course of using its investigatory authority to examine potential constitutional violations by state and local law enforcement. Additionally – and also for the first time – DOJ announced that the heightened scrutiny that it concluded applies to sexual orientation classifications also applies to classifications based on gender identity.

In immigration cases where a foreign partner in a same-sex binational relationship faced deportation, the February decision by DOJ appeared to cause immigration judges under DOJ concern about continuing deportations. And, for a short time, officials at the U.S. Citizenship and Immigration Services issued an abeyance on marriage-based green card applications filed by same-sex couples, though it was temporary and didn’t last long. In May, though, Holder took the rare step of sending a case involving a same-sex couple that had been pending in the U.S. Court of Appeals for the Third Circuit back to the Board of Immigration Appeals for further review. Then, observing the landscape, a Maryland immigration judge in June issued an order reopening the immigration case of Rodrigo Martinez – married to an American man – ”in the interest of justice.”

Also in June, the U.S. Bankruptcy Court for the Central District of California, in Los Angeles, released an opinion – signed by almost all of the more than 20 judges of the court – finding that DOMA unconstitutionally prevented a same-sex married couple from filing a joint bankruptcy petition.

As all this was happening, BLAG began defending DOMA in Golinski’s case and in others, such as Windsor’s in New York. When BLAG did so, however, it actually provided the administration with an opportunity. Now that there was someone – Paul Clement, the former solicitor general of the United States and one of the leading appellate advocates in the nation – defending DOMA, the administration did more than just decline to defend DOMA. It actually went on the offensive, taking aim at the law.

On July 1, DOJ responded to BLAG, with the government filing an unprecedented brief detailing the history of discrimination faced by gay, lesbian and bisexual people in America, including by the federal government itself. The brief, filed in Golinski’s case in response to BLAG’s motion to dismiss her claim for equal health insurance benefits for her wife, went on to detail why DOMA should be found unconstitutional. It is the single most persuasive legal argument ever advanced by the United States government in support of equality for lesbian, gay and bisexual people.

In the eight weeks since that filing, the fallout has continued to advance the legal case for LGBT equality in the courts – and, often, the administration has taken steps to help that process move quicker.

In the bankruptcy case, DOJ spokeswoman Tracy Schmaler wrote to Metro Weekly in July that it had adopted a new policy for such filings, writing, ”The Department of Justice has informed bankruptcy courts that it will no longer seek dismissal of bankruptcy petitions filed jointly by same-sex debtors who are married under state law.”

In the DADT case, the Ninth Circuit raised questions about the impact of the Golinski DOJ brief on its ongoing consideration of the LCR case – questions that will be debated when the appeal has its oral argument on Sept. 1.

In the immigration context, Department of Homeland Security Secretary Janet Napolitano adopted a new policy for deportation priorities Aug. 18, focusing on criminal and terrorist-threat cases – a change that a senior administration official said included considering same-sex couples to have a family connection that would make a foreign partner facing deportation a lower-priority case.

Then, on Aug. 19, DOJ filed a brief in Edith Windsor’s challenge in New York – one of the two cases that led to Holder’s original Feb. 23 letter – arguing that Windsor should win her case and receive the more than $350,000 tax refund that she has been denied because her marriage to her now-deceased wife was not recognized by the federal government.

Six months since Feb. 23, much remains unresolved. DOMA is still law; couples still face immigration questions and great uncertainty; DADT’s end won’t lead to equal benefits for same-sex partners of gay, lesbian and bisexual servicemembers; and the president still has not told the country whether he has finished evolving and now, again, supports marriage equality.

Nonetheless, the impact of the Feb. 23 decision by Obama and Holder cannot be denied – and may turn out to be one of the great moments in the history of the movement for LGBT equality. Their decision already has led to dramatic changes across the country and the federal government in the way that lawyers and judges see legal challenges brought by LGBT people – and, slowly but surely, in the way that LGBT people are able to live their lives.