Lacrosse is governed internationally by the 62-member World Lacrosse, which sponsors the World Lacrosse Championships once every four years. A former Olympic sport, attempts to reinstate it to the Olympics have been hampered by insufficient international participation and the lack of standard rules between the men's and women's games. Field lacrosse is played semi-professionally in North America by Major League Lacrosse and professionally by the Premier Lacrosse League. It is also played on a high amateur level by the National Collegiate Athletic Association in the United States, the Australian Senior Lacrosse Championship series, and the Canadian University Field Lacrosse Association.