Texas Higher Education and Creation Research, Part 28

Several sources are reporting that The Institute for Creation Research (ICR) is petitioning the Texas Higher Education Coordinating Board (THECB) to reverse its ruling, citing "viewpoint discrimination." The wire articles note that this opens the way for ICR to sue the Board, which has been a strategy the Institute has taken before.

I am trying to read about what "viewpoint discrimination" entails legally. My initial skimming suggests to me that ICR is going to have a very hard case to make that this is viewpoint discrimination (which is apparently a legal no-no) and not content discrimination (which is legally okay).