This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112c. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
According to 7.6.4 [expr.mptr.oper] paragraph 6,
The result of a .* expression whose second operand is a pointer to a data member is of the same value category (7.2.1 [basic.lval]) as its first operand.
This is incorrect if the member has a reference type, in which case the result is an lvalue.
Rationale (September, 2010):
There are no pointers to member of reference type; see 184.108.40.206 [dcl.mptr] paragraph 3.