> Assume that those who came before you had good reasons for their actions
There's a limit to that assumption, though. I'm always inclined to assume that people had reasons, and that they looked good at the time, but without knowing what those reasons are, there's no way to know if the reasons are as good now as they were then, even if you make the charitable assumption that they were good reasons at the time.
I would be a big fan of the idea that legislation had built-in turnover clauses, for instance, that required renewal every N years (for a value of N not much larger than the turnover rate of legislators). Which then means if you want something to persist, you would have to document your rationale for posterity, and convincingly argue that that rationale still applies.
> I'd be curious to see a strong legislative version of this - enshrining the spirit of the law in the text, and giving courts explicit rights to strike down laws which no longer fulfill their original intent.
I agree completely. Laws should state up front that "the purpose of this law is to ...", and for that matter explicitly state any other relevant considerations or side effects and whether they're considered beneficial, undesired, or simply neutral. That would mean there would have to be at least a pretense of a sensible motive, and that interpretations that don't serve that motive could be thrown out.
> The Aereo suit, for instance, shouldn't have happened under any kind of intent-based legal system.
It still could have, depending on the intent. The intent of copyright law, for instance, is supposed to be "we want more works produced, but we also want more works to enrich the public domain, so there's a tradeoff". The intent was never about authors and what they want; that's a means to an end. However, that rarely seems to be reflected in deliberations.