衡平法是如何发挥作用的？

H. Smith指出：

法律的简单结构容易被投机者利用……传统上，衡平法关注的是“欺诈边缘行为”（ “near fraud”），即接近欺诈界限、或很可能构成欺诈但无法被证实为欺诈的行为。

……传统衡平法的一个重要主题是打击机会主义行为。为此，衡平法需要超越事前明确的规则（the ex ante bright line rules），因为很难预料到所有规避的途径。

如果所有规避者都能轻易地钻过第十个漏洞，那么堵住十个漏洞中的九个也是徒劳的。衡平法采用事后道德标准（ex post moral standards），强调善意和告知，以道德为依据进行推理，其规则常常模糊而非明确。为了限制这种强大的工具，衡平法院只能对人而非对物的方式运用这些规则（in personam and not in rem），而且衡平法的实质原则也告诫人们谨慎以避免削弱法律。衡平法并非旨在根除一切机会主义行为，法院也认识到，除非法院保持警惕并阻止衡平法的不当介入，否则衡平法的原则和救济措施（尤其是禁令）本身可能会被机会主义的诉讼人利用。

我的简评：

1.

衡平法的规则主要体现为一种事后规则而非事前的规则。因担心某些行为包含滥用规则的可能性就一律禁止之，效率是低下的。普通法和衡平法是一体两面，都采取能行为发生之后再予以补救的事后策略（ex post strategy）。

2.

衡平法是对人（in personam ）发挥作用的。简言之，是在个案中发挥作用的。

3.

衡平法的规则是抽象的（原文用语是“模糊的”）。需要法官在个案中裁量行使，对法官提出了很高的要求。

附原文：

The simple structures of the law are open to exploitation by opportunists . . . Traditionally equity concerned itself with 'near fraud', which is behaviour that is close to the line of fraud or may well be fraud but cannot be proved as such. .

..A major theme of traditional equity was to counteract opportunism. To do so equity needs to go beyond the ex ante bright line rules, because it is difficult to anticipate all the avenues of evasion.

Plugging nine out of ten loopholes is hopeless if all the evaders can rush through the tenth. Equity employs ex post moral standards, emphasizes good faith and notice, couches its reasoning in terms of morals, and is sometimes vague rather than bright line. To cabin such a powerful tool, equity courts were only supposed to act in personam and not in rem, and the substantive doctrines of equity counselled caution in undermining the law. Equity was not designed to root out every last bit of opportunism and courts recognized that equitable doctrines and remedies, not least injunctions, themselves could be exploited by opportunistic litigants unless courts were on their guard and were willing to stay the hand of equity.

H. Smith, "Property, Equity, and the Rule of Law，in L. Austin and D. Klimchuk (eds), Private Law and the Rule of Law (Oxford University Press, 2014), pp.232-233.

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