Underscoring a dramatic turnabout in his own personal worldview, President Obama on Friday focused the microscope of government on what has only recently emerged as a national concern: the right of Americans to bypass biology and determine their own gender.

The transgender bathroom battle heated up as Republicans in North Carolina passed a state law in March barring transgender women from using the ladies’ room. But after North Carolina and the United States Department of Justice traded lawsuits this week, the fight went national on Friday, when the Department of Education and Justice Department sent what they called a “guiding” letter on transgender rights to the nation’s nearly 100,000 public schools.

Tying bathroom choice to sex discrimination under the Civil Rights Act is a poignant political shot across the bow. More deeply, the Obama administration’s decision to effectively tell schools that it's illegal to bar transgender people from the bathroom of their choice has started a legal battle where the Supreme Court – now ideologically split 4 to 4 – may have to arbitrate difficult questions around defining sex, gender, and identity.

Critics retort: If biology can be questioned, then whither the laws of "common sense"? Why should identity rights trump privacy rights?

As conservative columnist Cal Thomas wrote this week: “Are morals and ethics now up for grabs, depending on which group makes the most noise and promises the most votes?”

Yet to others, the issue is deeply symbolic of a fight for national ideals and human liberation. And by taking the bathroom issue from a constitutional arm-wrestling match with North Carolina to nearly every schoolhouse in the nation, Mr. Obama is, presidential historians say, pushing for a tipping point on a new frontier of civil rights. And as it did during other civil rights eras, the bathroom has become the gauntlet.

“There’s a sense that, for Obama, one of the larger meanings of the American experience is the expansion of rights to those groups that have been excluded,” says Bruce Miroff, a presidential historian at the State University of New York in Albany. “But there’s also a sense of political timing here, that transgender rights are becoming … a kind of natural follow-on to the struggle over same-sex marriage.”

The letter, issued by the US Departments of Justice and Education, captures a quickening political moment, marked in part by Obama's own evolution on gender-based civil rights. Same-sex rights were hardly on Obama’s agenda for his first four years. He didn't officially announce that he supported gay marriage until May 9, 2012, when he conceded that “I’ve been going through an evolution on this issue.”

He has now fully embraced it. He gave a shout-out to Seneca Falls, N.Y., the site of the first women’s rights convention, in his second inaugural address, after noting: “We, the people, declare today that the most evident of truths – that all of us are created equal – is the star that guides us still.”

In 2013, the Nation magazine suggested those words could amount to nothing more than “seductive rhetoric that lacks substance.”

As more recent administration moves prove, that’s no longer the case.

Just days ago, Obama proposed turning the iconic Stonewall Inn, the Greenwich Village bar where the gay rights movement galvanized in 1969, into a national monument. Attorney General Loretta Lynch’s statement this week to America’s estimated 700,000 transgender citizens that “We see you,” became the most forceful federal defense of transgender rights in US history. It also tipped states that Washington would deal forcefully with states that, in the administration’s view, continue to discriminate based on outward appearance and manners.

The move to force school districts to allow transgender students to use the bathroom of their choice was met with fury from some on the right. Republicans have raised concerns about Obama’s "imperial presidency" – his willingness to bypass Congress to take big national steps, including immigration reform, thawing relations with Cuba, pushing tough environmental regulations, and, now, putting US schools at the forefront of transgender rights.

"I don't think the president has the authority by himself to make that decision," North Carolina Gov. Pat McCrory told NPR Friday. He also said the framing this as a civil rights cause ignores concerns about privacy for children.

"The expectation of privacy that men and women, boys and girls have in a highway rest stop, in gym, a locker room after gym, or a shower, a showering facility," he said. "There's an expectation that the only other people will be the same gender as they are and that's the way we've been doing things for a long time."

Yet as Alvernia University historian Tim Blessing says, Obama “has a particular vision that he’s going to interpret, and there is a sizable body in the country – and I have no idea if it’s a majority – whom he is accurately reflecting, and which, in a democracy, he has a right to do.”

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If it’s not a majority, it’s close. According to a CNN/ORC poll out this week, 6 out of 10 Americans disapprove of laws like the one in North Carolina, which requires each citizen to use bathrooms that correspond to their gender at birth. Moreover, as recently as 2008, only eight percent of Americans were aware of transgender people around them, according to a survey done by the Human Rights Campaign. Today, that figure stands at 35 percent.

But it’s also potent political rallying call for Republicans and many older Americans, who are only half as likely to support transgender rights as those under 30. Moreover, as The Christian Science Monitor reported Friday, many Americans otherwise accommodating toward gender rights still balk at sharing bathroom and locker room space with those who have a different biological gender.