Proposed resolution (February, 2016):
Change 7.7 [expr.const] bullet 2.9.2 as follows:
A conditional-expression e is a core constant expression unless the evaluation of e, following the rules of the abstract machine (6.9.1 [intro.execution]), would evaluate one of the following expressions:
...
an id-expression that refers to a variable or data member of reference type unless the reference has a preceding initialization and either
it is initialized with a constant expression or
it is a non-static data member of an object whoseits lifetime began within the evaluation of e;...