Why aren't template specializations allowed to be in different namespaces?

Please, see what I am trying to do:

#include <iostream>
namespace first
{
 template <class T>
 class myclass
 { 
  T t;
 public:
  void who_are_you() const
  { std::cout << "first::myclass"; }
 };
}
namespace second
{
 using first::myclass;
 template <>
 class myclass <int>
 {
  int i, j;
 public:
  void who_are_you() const
  { std::cout << "second::myclass"; }
 };
}

This isn't allowed. Could you please, clarify why can't specializations be in different namespaces, and what are the available solutions? Also, is it something fixed in C++0x?

This would allow me for example, to specialize std::max, std::swap, std::numeric_limits, etc.. without resorting to undefined behavior by adding something to ::std::?

@AndreyT Here is how I though I would use it:

// my_integer is a class
std::numeric_limits<my_integer>::max(); // specialized std::numeric_limits for my_integer

Can this be done?