_ Part two applies to single-stall restrooms. D.C. requires these facilities be labeled gender neutral -- meaning for use by women or men, transgender or otherwise.
D.C.'s law also includes 18 other types of protections, including on the basis of disability, national origin, political party affiliation, race, age and religion.
"I don't see why it couldn't be emulated anywhere else," Imse said.
In North Carolina, HB2 requires people in government buildings and schools to use bathrooms that correspond to the sex on their birth certificates. The law has been called discriminatory but supporters argue it's a necessary measure for privacy and safety.
Here's what can happen with a bathroom law like D.C.'s:
1. Change unfolds slowly
In 2014, eight years after D.C. passed its bathroom laws, local government officials launched an awareness campaign called "Safe Bathrooms" -- a move made after some confusion about enforcement and business regulations. Still, D.C. bathroom use has not been without conflict.
Less than three weeks ago, for example, a transgender woman reported being called a homophobic slur and alleged that she was physically pushed out of a D.C. grocery store women's restroom by a security guard. Police charged the female security guard with misdemeanor assault and the incident is being treated as a suspected hate crime, according to the Washington Post.
In 2016, some businesses still don't comply with the original law. But progress is made, sometimes business by business. New businesses are denied opening permission if bathrooms don't comply.
Before opening his neighborhood bar and restaurant Public Option last year, D.C. business owner Bill Perry failed an initial inspection, in part because his building has two single-stall restrooms -- one labeled for men, the other for women.
"Those were left over from the previous occupant," Perry said. "I hadn't thought one way or the other but I learned. ... I was happy to go out and spend the approximately one dollar and buy new signs."
Perry put up two gender-neutral signs and later added a sign indicating one restroom includes a baby-changing table.
"To the best of my knowledge," he said, "there's been no issue whatsoever with any of the customers."
2. Safety issues not common
There have been no reported cases in D.C. of non-transgender people posing as transgender in order to access restrooms with criminal intentions, as has been feared by some proponents of North Carolina's controversial HB2 law, Imse said. The D.C. Metropolitan Police Department did not return a request from McClatchy for information.
Given D.C.'s record of no crimes related to the bathroom law -- other than transgender people at times facing harassment -- Imse says the safety argument for laws like HB2 "seems absurd."
Business leaders interviewed by McClatchy recently in D.C. agreed.
"I really don't understand why anybody is getting upset about this. From what I know, the cases that they're citing of men putting on wigs to stalk people in the bathroom, those aren't people that identify as transgender. Those are predators. And that's completely different," said Kyle Todd, executive director of one of D.C.'s economic development programs.
3. The difference is subtle
Crossing a state line into a jurisdiction with different bathroom laws may largely go unnoticed by most.
"Everywhere we went it was just very much standard operating procedure. ... It was just boys (or) girls," said Jay Pfeifer, a Charlotte resident who visited D.C. recently with his wife and two children, ages 5 and 8 at the time.
Nearly 20 million tourists visit D.C. annually, frequenting museums, restaurants and hotels.
The Pfeifers spent four days in Washington on what Pfeifer described in an interview as a "standard kids' Spring Break." The trip happened just days after North Carolina's legislature passed HB2.
"I'm kind of embarrassed that I didn't even notice (a difference)," said Pfeifer, who opposes HB2.
Pfeifer's youngest child -- his daughter -- has just recently been allowed to go into public restrooms without her mom accompanying her.
"It still makes me nervous if she takes too long, but that has nothing to do with (transgender people or HB2)," Pfeifer said.
4. Exceptions may still apply
Unique in that it's not a state but a federal district ultimately under the authority of Congress, D.C. cannot enforce its bathroom laws in some of the most-trafficked parts of the city. D.C. laws do not apply to federal government property, which includes the National Zoo and the popular Smithsonian museums on the National Mall.
Federal laws bar discrimination in public spaces based on sex but do not explicitly include gender identity as a protected class. The interpretation of those federal laws is the crux of the political and legal fight unfolding between states like North Carolina and the Department of Justice.
But the D.C. law does apply to restaurants, hotels and privately owned businesses also popular with tourists, like the kid-friendly International Spy Museum and the Newseum.
D.C. tourism officials told McClatchy they have no data on the impact on tourism concerning local bathroom laws.
Other jurisdictions with similar bathroom laws also have limitations while aiming to provide equality for transgender people.
For example, a Maryland state law bans discrimination on the basis of sexual orientation and sexual identity but includes exemptions for religious organizations, private clubs and schools. Maryland's law also puts restrictions on transgender people's use of locker rooms or places where it's common for people to disrobe.
In other states -- especially those without any specific bathroom laws -- public schools have used a mix of policies. Some allow bathroom use based on gender identity; others restrict use based on birth sex. Some provide alternative, single-stall rooms for transgender students -- which may not go far enough under new federal guidelines.
5. New policies take shape
As D.C. rolled out its bathroom laws, government officials set up new administrative processes for complaints, questions and enforcement.
A key question surrounding North Carolina's HB2 is enforcement and whether transgender people would be punished if they disregard the law. HB2 provides no penalty and has no enforcement provision.
But mostly, it seems, D.C.'s bathroom laws haven't caused a fuss, Todd said.
"You've probably been using the restroom with transgender people off and on for decades, and nobody's ever known," he said. "I just can't stress this enough: It's just not a big deal. There hasn't been a lot of wringing of hands and gnashing of teeth. It's just a bathroom."