Patent Judges Unconstitutional?

Prof. John F. Duffy argues:

Under 35 U.S.C. § 6, administrative patent judges of the Board of Patent Appeals and Interferences (BPAI) are appointed by the Director of the Patent and Trademark Office (PTO). That method of appointment is almost certainly unconstitutional, and the administrative patent judges serving under such appointments are likely to be viewed by the courts as having no constitutionally valid governmental authority.

Are Administrative Patent Judges Unconstitutional?, 2007
Patently-O Patent L.J. 21, http://www.patentlyo.com/lawjournal/2007/07/areadministrat.
html.

Now a party is making the argument in a petition for certiorari. Challenge to BPAI Appointments Moves to Supreme Court, Patently-O Patent Law Blog, April 16, 2008.

The National Law Journal reports on it in its upcoming issue: Marcia Coyle, Patent board's rulings in doubt: Appointment of judges questioned, Nat'l L.J., Apr. 28, 2008 (password needed to see whole article).