Reuven S. Avi-Yonah (Michigan) has posted The Case Against Taxing Citizens on SSRN.  Here is the abstract:

The US is the only developed country to tax citizens living permanently overseas on their worldwide income. This rule was created at a time when the income tax applied only to the rich and when some of the rich moved overseas to avoid the draft. We do not have a draft any more, the income tax applies to the middle class, and many more US citizens live permanently overseas for non‐tax reasons. In a globalized world, citizenship‐based taxation is an anachronism which should be abandoned.