It is sometimes claimed that celibacy became mandatory for Latin Church priests only in the eleventh century; but others say, for instance: "(I)t may fairly be said that by the time of St. Leo the Great (440–61) the law of celibacy was generally recognized in the West," and that the eleventh-century regulations on this matter, as on simony, should obviously not be interpreted as meaning that either non-celibacy or simony were previously permitted. However there is abundant documentation that up to 12th century many priests in Europe were married and that their sons would often follow their path which made the reforms difficult to implement.