The Nazir's Allowance to Become Tamei

It is evident from the Rambam in Hilchos Nezirus (7:12) that the reason that a nazir may become tamei to a meis mitzvah is because of the mitzvah of burial. However, from Tosfos, it would seem that there is a different reason. Tosfos writes that it is permitted for the nazir to move the corpse from the sun to the shade. This would indicate that the allowance for the nazir to become tamei is not on account of the mitzvah of burial, but rather it is due to the obligation of respecting the dead.

The Rogatchover Gaon notes the following distinction between the two reasons: If a father imposed nezirus upon his son, and the son, as a minor, comes upon a meis mitzvah. If the reason for the permission to becoming tamei is because of the mitzvah of burial, a minor who is not obligated in mitzvos, would not be allowed to become tamei to the corpse. However, if the allowance is based upon respecting the dead, the minor would also be obligated to bury him, for he is also responsible to see that a corpse does not lie in degradation.