**We** can't.
**Congress** can, should we elect the people to Congress who are interested in doing that.
So far, no matter the political identities of who we elect to Congress, the law hasn't been changed in that way, though, probably because the home mortgage deduction is really popular.
But that doesn't change where we are today, with the peoples' representatives having already appropriated the money expected to be collected from these loans.
Except that if you actually read the law, that's not what it says, and that's the core of this court case.
The act does not explicitly empower the president to write off student debt.
You can pull up the text of the act to see that for yourself.