Green Vine Mountain is considered a thorn on the territory of the Heaven and Earth Gang, but for some unknown reason, the Sect Master of the Heaven and Earth Gang does not seem to care about this thorn in their side.
The reason for this is something that all cultivators can guess—it's all because of the annual Green Vine Conference held on Green Vine Mountain, the grandest event of the mountain. Historically, the champions have always been members of the Heaven and Earth Gang. It is rumored that, after being acknowledged by the Master of Green Vine Mountain, the champion's Cultivation Base will greatly increase.
Of course, these are just rumors. The real situation is well understood by many—it's likely that the Heaven and Earth Gang has reached some agreement with the Master of Green Vine Mountain, which is why they are allowed to exist here.