Donald Trump’s new memorandum to exclude undocumented immigrants from the next round of congressional apportionment is morally repulsive, illegal, and impossible. It is repulsive because it borrows the logic of the notorious Three-Fifths Clause to declare that undocumented immigrants are not full “persons” under the Constitution. It is illegal because it seeks to exclude these immigrants from a state’s population when counting how many seats each state gets in the House of Representatives, which violates the Constitution. And it is impossible because there is no way that the government can count undocumented immigrants with any accuracy by the December deadline.

None of these problems will stop Trump from trying to rig the census to strip House seats from states with large undocumented populations. Even if this scheme fails, however, the memo will do insidious damage to the bedrock principle that all people count. Trump has formally endorsed the notion of excluding noncitizens from the redistricting process, an idea that red states are already exploring to boost the electoral power of white, rural voters at the cost of diverse urban centers.