bonuses

[Sanford Levinson]

What prohibits Congress from passing a law saying either 

a) No contract between any bank or other entity receiving federal
bailout funds and any employees regarding the receipt of bonuses shall
be honored, save with the approval of the Secretary of the Treasury or

b) any bonus received after December 1, 2008, by any employee of any
bank or other entity receiving federal bailout funds as of that date
shall be taxed at the rate of 100%?

I presume that the bankers would cite Blaisdell (a state case, of
course) with regard to the first.  I believe that the contract clause
has been incorporated against the feds with regard to its own contracts,
but what about a class attempt to "impair the obligation of contracts"?
Even if one constructs (our of whole cloth?) an argument against federal
impairment of private contracts, what about the confiscatory taxation?
On what theory is that unconstitutional?  

sandy