Ted Cruz’s former law teacher Alan Dershowitz has called the Texas senator’s questioning of Supreme Court nominee Judge Ketanji Brown Jackson "absurd".

       At Ms Jackson’s confirmation hearing on Wednesday, Mr Cruz asked how she could determine standing to challenge a gender-based rule given she could not define what a woman is, adding what would happen if he changed his race as easily as changing genders.

       "Tell me, does that same principle apply to other protected characteristics? For example, I’m a Hispanic man. Could I decide I was an Asian man?" Mr Cruz asked.

       "Would I have the ability to be an Asian man and challenge Harvard’s discrimination because I made that decision?”

       Ms Jackson said she would decide standing in such a transracial case by listening to arguments made by parties, consider the precedents, and constitutional principles involved.

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       Mr Cruz’s former law professor, however, said the question was "absurd".

       "I hope he didn’t learn them from me, he was my student, where he said, ‘If a man has the right to choose to be a woman, will I as a Latino person have the right to choose to be Asian?’," Mr Dershowitz said on a Rumble live stream.

       "No, no you don’t, you can’t change into somebody who’s Asian. You can marry somebody who’s Asian and live an Asian life and be part of Asian culture. But no you can’t do that."

       He added people could convert, like being a Catholic converting to being Jewish, which is both a race and a religion. Or vice versa. But there are certain things, like being Hispanic or Asian, that can’t be changed.

       "We used to think that gender was one of them. It turns out it’s not. It turns out you can change gender," he said.

       Mr Dershowitz taught Mr Cruz at Harvard Law School, and the case Mr Cruz cited during his questioning was a pending allegation that Harvard University’s affirmative action policies violate the rights of Asians.

       Both double-downed after the confirmation hearing, with the student taking to Fox News and the teacher Newsmax to plead their case.

       "She is probably the first Supreme Court nominee in the history of our country who is unable to answer the question of what is a woman," Mr Cruz said on Fox News after Jackson told the hearing she wasn’t a biologist and thus couldn’t define what a woman is.

       Mr Dershowitz said Mr Cruz, previously described as one of the best students he ever had, told Newsmax that he did not "distinguish himself" comparing transgender people to transracial people.

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       There’s a big difference. If a Latino man marries an Asian woman or vice versa and decides to live an Asian life, you can do that. But you’re still a Latino," he said.

       "But if a man decides to become a woman or a woman decides to become a man, hey, welcome to the 21st century.”