Originally it was never supposed to be instantaneous travel hence the quotation marks, but I do agree that seemed very vague and could be easily exploited into god modding.
If I assume you are talking about Murus, then specialized space-time manipulators would yank anyone trying to evade Murus out of FTL before they could get past Murus. If they were to manage to get past it, Cheyenne is adequately able to defend itself until the Murus defense fleet would arrive...