This effect it may be thought will not necessarily take place: since a ward may have two guardians. One man then is guardian by right: another man comes and makes himself so by usurpation. This may very well be, and yet the former may continue guardian notwithstanding. How then (it may be asked) is he divested of his guardianship?—The answer is—Certainly not of the whole of it: but, however, of a part of it: of such part as is occupied, if one may so say, that is, of such part of the powers and rights belonging to it as are exercised, by the usurper.

IPML Chapter 16 Section 3 Part 3