I said a version of this before but I’ll say it here:
You can say "POTUS has the unilateral ability to cancel all federal student debt" and you can probably find law professors who will agree with you; however, you'd need a circuit court judge to agree and that would likely have to be a Trump appointee. Then need SCOTUS to agree with you and there's currently a 6-3 conservative lean.
Constitutionally, Congress has the “power of the purse”, but they granted the executive the power to cancel student debt via DoED in the Higher Education Act of 1965. However, using that power to cancel debt has never been attempted for an amount as large as what's being proposed (up to $50k per person); moreover, when it has been used it was in narrower circumstances (fraud, school closure, permanent and total disability, etc.), but never for blanket student debt relief.
I think this leads to an obvious court challenge asking some version of the following, did Congress give POTUS/DoED unchecked unilateral power to cancel student debt with the Higher Ed. Act? When I consider the current SCOTUS view of executive agencies, I believe it would be a 5-4 decision, assuming Roberts decides to play nice for the optics, holding that the executive branch does not have unchecked unilateral power to cancel all federal student debt.
This is why I believe Biden opposes using executive action but has no issue with signing a bill that accomplishes the same thing. The thing I wonder is why $10k is his cut-off? I assume that would be in line with previously canceled amounts because it otherwise seems rather arbitrary. Anyway, this is ultimately the job of Congress, Schumer and the Senate are trying to push this responsibility on to Biden when they should act themselves. We need wide-sweeping education reform anyway; federal student loans have been frozen and they aren’t accruing interest so it’s not like we’re asking them to act on this tomorrow. We all know infrastructure and voting rights would take priority. Manchin is a proponent of both and either would likely be a flashpoint where the filibuster could get altered (Merkley's
plan is alright).
All of our Senators are currently on recess, so I think giving them a call and telling them to act on student debt instead of trying to pass the buck to Biden is probably the play.