In contact sports, the primary issue of concern with regard to competition between the sexes, is one of safety and fair competition. In general, sports have separate teams and competitions for men and women because at higher levels of skill and competition, the average male athlete has greater muscle mass per unit volume of body tissue (and therefore greater strength) than the average female athlete. Since most sports involve overcoming the resistance of a mass or propelling a mass through space, strength and muscle mass are critical variables with regard to designing fair competitions. Therefore, pitting males versus females would in most cases, give males a significant strength advantage.
However, it is also important to note that the physical differences within the sexes are greater than the difference between the sexes. There will always be some women who can match up and compete against some men. Weight classes work for men in sports such as wrestling and boxing because there is an assumption that well-trained male athletes of the same weight have similar muscle masses. We also know that another important variable is the length of a boxer's arms.
When you look at all of these variables, it is possible to envision a fair competition between skilled men and women in boxing if the women has a longer levers and a higher than average amount of muscle mass.
The position of the Women's Sports Foundation is that boxing is a dangerous sport in which sport governing bodies should continue to develop new safety measures to protect male and female participants. As long as competing athletes are matched by ability, muscle mass and other standardized physical variables critical to success in the sport, competition between males and females should be permitted.