[Moved to DR at the November, 2014 meeting.]

Proposed resolution (November, 2014):

This issue is resolved by the resolution of issue 1838.

According to 9.8 [basic.namespace] paragraph 1,

The name of a namespace can be used to access entities declared in that namespace; that is, the members of the namespace.

implying that all declarations in a namespace, including definitions of members of nested namespaces, explicit instantiations, and explicit specializations, introduce members of the containing namespace. _N4868_.9.8.2.3 [namespace.memdef] paragraph 3 clarifies the intent somewhat:

Every name first declared in a namespace is a member of that namespace.

However, current changes to clarify the behavior of deleted functions (which must be deleted on their “first declaration”) state that an explicit specialization of a function template is its first declaration.