I live close to a Benedictine monsastery and as far as I know only Benedictines can bless them. It has to do with the exorcism power of the medal.
Maybe the Benedictines are possessive of this blessing, but I have been told by them and by my parish priest that the St. Benedict medal needs to be blessed by a Benedictine.
I read the pope changed it in the sixties. Pope Paul. I am watching my team play football will investagate later. luv ya big sis! Praise Jesus!