I hope this is the right forum to ask, I have are two questions in regards to Popes and Vatican laws.
1) Roman Catholic preists haven't always had to remain celibant, there were times when they could marry. Celibacy was introduced by a Pope around the 13th or 14th centuries.
Celibacy was strongly advocated by Paul in 1 Corinthians 7, so it can hardly be said that the Catholic Church "invented" it. As a Church discipline, however, it was first imposed in Spain by the local Council of Elvira in 306 AD, and Church-wide by the 2nd Lateran Council in 1139 AD.
A goodly part of the reason it became such an issue was to prevent the practice of primogeniture in the Church. (Primogeniture is when the oldest son inherits his father's business, and in the case of a priest, this meant the parish church.) The Church recognized that simply because somebody was the son of a priest, that didn't automatically mean that the son was suitable to be a priest himself, so this discipline was imposed to prevent clergy from producing children. There was also the fact that the lands, buildings, moneys, etc. that belonged to the Church needed to stay with the Church, because they belonged to the entire people of God as a whole, and not be inherited by the children of clergy---so celibacy was also a way of maintaining stability and unity within the structure of the Medieval Church.
2) Same for eating fish on Fridays, I have heard it was introduced by a Pope to help an ailing Italian fishing industry.
You heard an ancient anti-Catholic canard that goes back to the 17th century. Meat was indeed forbidden on Fridays, but it had nothing to do with any Pope helping out the European fishing industry; since meat was out, fish merely became the permitted food by default.
Abstinence from meat on Fridays is mentioned as far back as Clement of Alexandria and Tertullian (both late 2nd century). It was strongly encouraged by the Council of Toledo in the 5th century, by Pope Nicholas I in the 9th century, and Pope Innocent III in the 12th. The practice itself was tied in with the development of the Lenten fast, which slowly spread throughout the Church after the late 2nd century; certain foods were to be abstained from, usually meat, fowl, butter, eggs, milk, and cheese. Pope Alexander VII removed the ban on eggs, butter, milk, and cheese in 1666, thus reducing the abstinence to meat and fowl. Fridays were seen as penitential days, since Christ was crucified on a Friday, and meat was not to be indulged in. Fish was permitted, but since there was no such thing as refrigeration or rapid transport, only the people living near the coast or close to lakes or streams would have access to marine products.
Since the 2nd Vatican Council, meatless days have been limited to Ash Wednesday, Good Friday, and all Fridays during Lent.
