Before I Make A Fool of Myself...a Question

Dear All,

I'm a professor at a major university in the U.S., and I'm a conditional permanent resident by marriage (about to be unconditional). I came across a postgraduate fellowship for a year that states the following:

Applicants must be able to provide evidence of U.S. citizenship or unconditional permanent residency status at the time of hire.

I've never seen any job or fellowship ask for unconditional permanent residency. Is it legal to differentiate between conditional and unconditional permanent residents for the purposes of fellowships and/or jobs? I'd imagine it wouldn't be, but I wanted to ask before I inform them. There's some irony given that it's a fellowship geared towards diversity in the academy!

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