I can find no better way to explain it that to quote Gordon Farquhar from your linked page.
The decision by Wada's foundation board was widely expected. It follows a week of increasingly heated exchanges between the two organisations. The BOA believes the by-law is an eligibility rule, and that it has the right to decide who can pull on the GB vest at the games. Wada says the BOA rule amounts to an additional sanction. If the BOA loses its challenge to the doping agency's decision, it will have to rethink the by-law which has overwhelming support among British athletes, and previously excluded the likes of Dwain Chambers from taking part in the London games.
Basically, Britain bans drug cheats from the Olympics for life. Everybody else sets time limits. And some of the cheats don't like our rules and will do anything to appear next year.