Beayf,
However, the legal system of the Church was, like civil law, based on Roman law. The reason that the application of the Canons today may seem more like a common law system as opposed to traditional Roman system which gave it birth is that we no longer have the Councils to keep the Canons current, thus their applications are often viewed as outdated and hence not strictly applied. However, the principle behind our Canonical system is that the Canons be based on Eternal Truths. However, the essence of the Roman legal influence survives in our canons, though it is difficult to fully apply it without a modern codification, but one important element of a 'civil law' system that is applied in our Canonical Tradition (though we probably actually adhear to it in practice for firmly than any other 'civil law' system) is that past precedents (especially instances of the use of +++¦+¦+++++++++¦+¦) can not be used to justify a canonical decision.
One example of this is in the case of Marriage between the Orthodox and Heterodox, there have been attempts to argue that it is acceptable in America based on past precedents, we have been doing it for decades, but this argument has been rejected in synod of the Oecumenical Throne and it was made clear that each time such a marriage is allowed it is a decision that is neither justified by past occurrences nor does it jusitfy future occurrences of the breach of the canon (Trullo 72), but rather it is only a one-time occurrence for the pastoral needs of that specific situation, in principle a decision that should be independently evaluated for each such marraige request, and a new ruling given by the bishop independent of all past rulings along these lines. The decisions of the Councils are regarded as absolute in Canonical matters, and can only be overturned by a Council of Equal or Greater authority, and no lesser authority can establish a common practice to the contrary (it doesn't matter if we've been doing it for ten years or a thousand years). Though we do accept interpretations of the Canons, these interpretations should be based on the decrees, actions, and thinking of the council itself and should not bring into account precedents and custom. It is for this reason that most the bishops in the world are quite concerned with our casual acceptance of Marriage between the Orthodox and Heterodox, and why it has been placed on the list of issues for the Great and Holy Synod.