Answer: One possible way to rephrase the phrase is “The rule becomes a dangerous tool, waiting for any power that can make a convincing case of a pressing necessity.”
Explanation: The phrase implies that the principle, or the rule, is not a fixed or absolute one, but rather a flexible or relative one that can be used or abused by different authorities for different purposes. The phrase suggests that the principle is not applied consistently or fairly, but rather selectively or arbitrarily, depending on the situation and the interests of the authority. The phrase also implies that the principle is not a benign or harmless one, but rather a harmful or dangerous one that can cause damage or harm to others. The phrase compares the principle to a loaded weapon, which can be used to threaten, coerce, or harm others. The phrase also suggests that the authority does not need to have a valid or legitimate reason to use the principle, but rather only a plausible or convincing one that can justify their actions in the eyes of others. The phrase also implies that the authority can use the principle whenever they feel an urgent need, which may not be a real or objective one, but rather a subjective or fabricated one. The phrase conveys a sense of cynicism and distrust towards the principle and the authority that uses it.
Hope this helps, and have a great day! =)