>>> df = pd.DataFrame(np.ones((10, 3)), columns=list("ABC"))
>>> df.index = pd.MultiIndex.from_product([range(5), list("AB")])
>>> df
       A    B    C
0 A  1.0  1.0  1.0
  B  1.0  1.0  1.0
1 A  1.0  1.0  1.0
  B  1.0  1.0  1.0
2 A  1.0  1.0  1.0
  B  1.0  1.0  1.0
3 A  1.0  1.0  1.0
  B  1.0  1.0  1.0
4 A  1.0  1.0  1.0
  B  1.0  1.0  1.0

>>> values = ["B", "A"]
>>> idx = pd.IndexSlice
>>> subset = df.loc[idx[:, values], values]
>>> subset
       B    A
0 A  1.0  1.0
  B  1.0  1.0
1 A  1.0  1.0
  B  1.0  1.0
2 A  1.0  1.0
  B  1.0  1.0
3 A  1.0  1.0
  B  1.0  1.0
4 A  1.0  1.0
  B  1.0  1.0