[AZLiberty]

who gave him the authority to grant citizenship in the first place?

This Quora response says the president only has authority to grant "honorary citizenship", which isn't the real thing.

https://www.quora.com/Can-a-US-President-grant-any-person-US-Citizenship-directly-if-he-or-she-wishes-to.

[Cletus.D.Yokel]

So, they get a US passport, then?
You know...under Obama.