ScaredBear Boys are not allowed to join guiding - it is a girls only organisation, and has every intention of remaining that way.
To be honest the whole issue is a bit difficult. Firstly, it is important to remember that despite their similarities, Guides and Scouts are completely separate organisations. They do cooperate on occasion, but in a way saying that "Scouts lets boys in so Guides should let girls in" is like saying "CoE churches now have female vicars, so RC should too". Maybe they should, and maybe they shouldn't, but what one organisation decides to do it not relevant to what the other decides, really.
Secondly, I can completely understand why girls want to join Scouting - it is generally far more adventurous and exciting than Guiding - certainly in the younger years. Guiding has lots of rules and is really H+S mad, whereas Scouting leaves a bit more room for common sense and sensible risk taking. So because Guiding has decided to take a girls only route, does that automatically mean that girls should be denied the great things Scouting has to offer?
Also - in my experience Scouting remains a very male oriented activity, and girls have slotted into that rather than Scouting changing greatly to admit them. I think Guiding would have to change a lot to be appealing to any boys at all.
It is interesting to note that many of the younger scouting units are now being run by women, and would have to close altogether if females were not allowed to participate. And it doesn't make sense to bar female participants if the unit is being organised and run by females - because then it isn't a "male space" anyway.
Just a few of my thoughts - and to be honest I find it hard to justify it completely happily to myself. For the record I am a Rainbow and Brownie Leader, and a regular assistant at Beavers.