Fox News host Brian Kilmeade gets a tough lesson on what the Constitution actually says, and he's not happy about it.

Fox News is very upset over California’s census lawsuit, so it was quite a shock to learn, live on the air, that the law is on the Golden State’s side.

On Tuesday, the “Fox & Friends” gang spent a good part of their morning fretting over California’s attempt to block inclusion of a citizenship question on the 2020 census.

While debating the issue with Fox News legal expert Judge Andrew Napolitano, co-host Brian Kilmeade brought out the big guns, attempting to settle things with a reading of the U.S. Constitution.

“All right, the U.S. Constitution, Article 1, Section 2, Judge, is? Requires the census count everyone in the U.S!” Kilmeade said.

“Count!” Napolitano replied. “Not ask how many toilets you have or what your ethnic background is, but count. How many people live in the house?”

“Even if they’re here illegally?” Kilmeade asked.

“Yes,” Napolitano answered.

“So the Constitution might be on California’s side?” Kilmeade asked.

“Yes,” Napolitano said.

Napolitano is usually as partisan as the other Fox contributors and hosts, but occasionally, he delivers uncomfortable truths to Fox News viewers. In this case, he’s delivering the uncomfortable truth that the census is about counting people, not citizens, to the Fox hosts themselves.

Experts say the citizenship question is an attempt to undercount people in urban areas, and shift power to more rural, Republican-friendly areas. Former Attorney General Eric Holder has said his group, the National Democratic Redistricting Committee, also will sue over the citizenship question.

The census is a major issue for American democracy, as it plays a huge role in determining congressional maps. When Republicans swept the midterms in 2010, it enabled them to gerrymander huge advantages for themselves following that year’s census.

Now faced with a blue wave in 2018 and perhaps even 2020, Trump and the Republicans are doing everything they can to keep as much of the map rigged in their favor as possible. But Democrats are already winning challenges to GOP rigging, and even Fox News seems to think this census issue will go their way.