What is the Ruling on Calling Oneself Maliki or Hanbali?

What do you want him to say? There is no harm in him saying, "I am Hanbali, I am Shafi'i, I am Maliki" These are Madhhabs of Ahlul Sunnah, and denying a Madhhab of Ahlul Sunnah is not permissible. But you should not say, "There is no truth except in the Hanbali Madhhab", this is impermissible. As for saying that the four Madhhabs are all Madhhabs of Ahlul Sunnah and goodness, then there is no harm in this.