istream& operator>>(istream& is, Card& d)
{
std::map<std::string,Card::Rank> mr;
std::map<std::string,Card::Suit> ms;
mr[std::regex("/two/i")] = Card::TWO;
mr[std::regex("/three/i")] = Card::THREE;
mr[std::regex("/two/i")] = Card::FOUR;
mr[std::regex("/two/i")] = Card::FIVE;
mr[std::regex("/two/i")] = Card::SIX;
mr[std::regex("/two/i")] = Card::SEVEN;
mr[std::regex("/two/i")] = Card::EIGHT;
mr[std::regex("/two/i")] = Card::NINE;
mr[std::regex("/two/i")] = Card::TEN;
mr[std::regex("/two/i")] = Card::JACK;
mr[std::regex("/two/i")] = Card::QUEEN;
mr[std::regex("/two/i")] = Card::KING;
ms[std::regex("/clubs/i")] = Card::CLUBS;
ms[std::regex("/diamonds/i")] = Card::DIAMONDS;
ms[std::regex("/hearts/i")] = Card::HEARTS;
ms[std::regex("/spades/i")] = Card::SPADES;

string srank, ssuit;
char c1;

if (is >> srank >> c1 >> ssuit)
{
    if (c1 == 'of')
    {
        Card::Rank rank = mr[srank];
        Card::Suit suit = ms[ssuit];
        d = Card(rank, suit);
    }
    else
    {
       is.clear(ios_base::failbit);
    }
}

return is;
}

error C2679: binary '[' : no operator found which takes a right-hand operand of type 'std::basic_regex<_Elem>' (or there is no acceptable conversion)
      with
      [
          _Elem=char
      ]
      c:program files (x86)microsoft visual studio 11.0vcincludemap(173): could be 'Card::Rank &std::map<_Kty,_Ty>::operator [](std::basic_string<_Elem,_Traits,_Alloc> &&)'
      with
      [
          _Kty=std::string,
          _Ty=Card::Rank,
          _Elem=char,
          _Traits=std::char_traits<char>,
          _Alloc=std::allocator<char>
      ]
      c:program files (x86)microsoft visual studio 11.0vcincludemap(190): or       'Card::Rank &std::map<_Kty,_Ty>::operator [](const std::basic_string<_Elem,_Traits,_Alloc> &)'
      with
      [
          _Kty=std::string,
          _Ty=Card::Rank,
          _Elem=char,
          _Traits=std::char_traits<char>,
          _Alloc=std::allocator<char>
      ]
      while trying to match the argument list '(std::map<_Kty,_Ty>, std::basic_regex<_Elem>)'
      with
      [
          _Kty=std::string,
          _Ty=Card::Rank
      ]
      and
      [
          _Elem=char
      ]

etc.

#include <cctype>

static inline void stringToLower(std::string &s) {
    for (uint i = 0; i < s.size(); ++i) {
        s[i] = tolower(s[i]);
    }
}

istream& operator>>(istream& is, Card& d)
{
    std::map<std::string,Card::Rank> mr;
    std::map<std::string,Card::Suit> ms;
    mr["two"] = Card::TWO;
    mr["three"] = Card::THREE;
    ...
    mr["king"] = Card::KING;

    ms["clubs"] = Card::CLUBS;
    ...

    string srank, ssuit, c1;

    if (is >> srank >> c1 >> ssuit)
    {
        stringToLower(c1);
        if (c1 == "of")
        {
            stringToLower(srank);
            stringToLower(ssuit);
            Card::Rank rank = mr[srank];
            Card::Suit suit = ms[ssuit];
            d = Card(rank, suit);
        }
        else
        {
            is.clear(ios_base::failbit);
        }
    }

    return is;
}

static std::map<std::string,Card::Rank> createmr() {
    std::map<std::string,Card::Rank> mr;
    mr["two"] = Card::TWO;
    mr["three"] = Card::THREE;
    ...
    mr["king"] = Card::KING;
    return mr;
}

static std::map<std::string,Card::Rank> createms() {
    std::map<std::string,Card::Rank> ms;
    ms["clubs"] = Card::CLUBS;
    ...
    return ms;
}

istream& operator>>(istream& is, Card& d)
{
    static std::map<std::string,Card::Rank> mr = createmr(); // note `static` keyword
    static std::map<std::string,Card::Suit> ms = createms();
    ...
}

static std::map<std::string,Card::Rank> mr = createmr(); // note `static` keyword
static std::map<std::string,Card::Suit> ms = createms();

istream& operator>>(istream& is, Card& d)
{
    ...
}