Many states, which includes California and might include New York, have neither reciprocity statutes or procedures for issuing concealed carry permits to non-residents. I.e., those states allow their own residents to obtain concealed carry permits, but won’t allow non-residents to do so. This is a violation of both the 14th Amendment’s equal protection of the law provision, and of the constitutional right to travel.
I believe that this is being challenged in one of the many cases working their way through the legal labyrinth in Kalifornia.
Governor "Moonbeam" Brown just signed a law outlawing open carry. Given the fundamental character of the right to bear arms, he has just helped shape the outcome of this case greatly.