CU is talking about illegal aliens, not immigrants.
  
***IRS
-Immigrant-
An alien who has been granted the right by the USCIS to reside permanently in the United States and to work without restrictions in the United States. Also known as a Lawful Permanent Resident (LPR)

-Illegal Alien-
Also known as an "Undocumented Alien," is an alien who has entered the United States illegally and is deportable if apprehended, or an alien who entered the United States legally but who has fallen "out of status" and is deportable.
https://www.irs.gov/individuals/international-taxpayers/immigration-terms-and-definitions-involving-aliens

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And unlike anyone else who is not a resident the state, these illegal aliens are paying instate rates. Out of state is the full costs, Instate is 'assisted' tuition costs.

Example:
CU BOULDER TUITION

ENGINEERING 
InState tuition ---------$7,842 

ENGINEERING 
Out of State tuition ---$18,645

https://bursar.colorado.edu/tuition-fees/tuition-and-fees-rate-sheets/