Believe me, I am not anti-law. :) Yes, we need some constraints to ensure our freedom. But, as with a repressive government, it can go too far. That's why I can't see the opposite of constraint as being slavery. On a "freedom" scale, I would think that they would not be equally apart from zero. Some constraint would be on the freedom side, but full constraint would be at the very end of the slavery side.
We should distinguish between legal constraint -- which ensures freedom and physical constraint -- which enslaves. Still if you remove law, you are left with rule of force and that means that some end up in chains.
Back to exegetics, the fundamental rule I am referring to is continuity of understanding since apostolic times. If, for example, one wants to read "all have sinned" in a way that makes Our Lady a sinner, he needs to not merely read the phrase itself, but also explain why no one for 1500 years read the passage in that way (early speculation of sinfulness of Mary were based on the verse where she did not appear to understand Christ's mission following His discovery in the temple). This tends to be the universal problem for Protestants, -- that apart from some very tendentious reading of St. Augustine, Protestant ideas have no patristic support.