Michael Henry Ishitani (Yale Law School & History Department) has posted What Does Impeachment Disqualification Mean and Does It Have a Remedy? on SSRN. Here is the abstract:
Article I, Section 3, clause 7 impeachment disqualification is assumed to be permanent and without remedy (outside Constitutional amendment). Neither text, history, nor doctrine compel this understanding. The Senate retains the constitutional authority both to impose a merely temporary disqualification and to remove the disqualification penalty.
Indeed, the reigning assumption is deeply problematic constitutionally. Structurally in that is cuts off democratic choice. Precedentially in that it limits what the Supreme Court has recognized to be the free prudential discretion of the Senate and has zero basis in actual Senate procedure. Ethically in how it strikes uniquely against Marbury’s and our general ubi ius remedium commitment to all injuries (including infringements on legal rights) having some constitutional if not solely legal remedy (aka political action even if can’t be supplied by judicial review). Prudentially in how it creates problems for maintaining the democracy and making impeachment workable for the Senate. Historically in how it cuts against all antecedent disqualification forms in the Western tradition, all of which seem to include some mode of remedy.
Our assumption of irremediability would therefore seem to require a clear textual command, which it lacks. Nor can we simply import judicial res judicata to impeachment. Contra Berger, impeachment and disqualification does not give rise to a due process claim justiciable in the Courts. However, it does create a constitutionally cognizable injury that the Senate has the political prudential authority to correct.
Congressional pardon and senatorial coram nobis offer the strongest constitutional models for remedying disqualification. Senatorial coram nobis in particular presents the radical possibility of reversing not only a disqualification penalty but the underlying impeachment removal decision. This gets at the paradoxical heart of impeachment, in its dual nature as both law and politics.