The Netashi govermnent and the Nechisti Order had an agreement, that they should not interfere in each other's business. This arrangement by the 2370s had been in place for centuries.
The shrine itself was protected by a biogenic field, which could cause massive neural damage to anyone who attempted to cross it unprepared. The Brothers knew a ritual that allowed them to pass through unharmed, but where sworn to secrecy.
In 2373, Kes encountered the field and fell into a coma-like state. Captain Janeway went through the Nechisti rituals in an effort to save her. After three days of grueling trials and exposure to a hallucinogenic toxin, the captain believed she had the answer. However, it was only when she abandoned her scientific approach and embraced a blind faith that she successfully penetrated the field and returned Kes to health. (VOY: "Sacred Ground")