the heir has had seisin after the death of the ancestor whose seisin is sought, because  if the heir, when he once has seisin [and] has made gifts, could then recur to the  assise, he could nullify gifts properly made by him.1
What kind of seisin bars the assise.
 [We thus must see what kind of seisin bars the assise and what does not. It is clear  that if seisin is momentary,2 so that the tenant could not have made gifts and alienations  in so short a time, or if he was within age so that his gifts ought not to hold,  or if he [was in] for a short time after the death of his ancestor, by intrusion or  disseisin, and was then quickly ejected,3 or the disseisee recovered against him by an  assise of novel disseisin, that the heir will have the assise of mortdancestor despite  such seisin, [because such seisin as he had is proved void or wrongful,] not only  because the intrusion was short, but because during it no gift, alienation or change  of possession was made by the heir, and if anyone was ejected he recovered4 his  seisin as fully and completely as he lost it. But [quaere] if, when the heir afterwards  claims by assise of mortdancestor and it is objected against him that he does  not merit it, because he usurped to himself without judgment and on his own authority  what he ought to claim by the assise, whether this exception ought to bar him?  [I do not see why not.]5 If one puts forward the exception of seisin had earlier he  must prove two things: that the heir has been in seisin and has made gifts while he  was in seisin, and was of such an age that the gifts cannot be revoked or nullified,  otherwise the exception will not be good. If the heir puts in a denial, the truth will  be declared by the assise taken in the manner of a jury. If seisin had while [the heir]  was below age is objected against him, it will not hurt him, because, despite such  seisin, if he makes gifts under age he may revoke them by an assise of mortdancestor,  a writ of entry or a writ of right, as he chooses, [whether he makes the gift [or] his  guardian or another,]6 unless he has confirmed the gifts on reaching full age. He will  not have the assise of novel disseisin against such donees because, though under age,  he withdrew freely and of his own volition. But if the guardian makes a gift while the  heir is within age, the heir will have an assise of novel disseisin and all the other remedies  aforesaid. Note that seisin [taken] earlier bars the heir from an assise of mortdancestor,  no matter what