How has it been possible to interpret the The Commerce Clause to justify so many and so varied exercises of federal power? I fully understand the political rationale behind this development (given how hard it is to change the Constitution), but it just seems to be obvious that it is objectively wrong to interpret it in such a broad manner. Even if you don't subscribe to original intent and consider the text a "living document", one should assume that there are some limits to how far you can stretch the Constitution.
A verdict like
Wickard vs. Filburn seems to be completely unreasonable. So did the justices basically just rule based on their own political views?
I have found this list (on a right wing site, but it seems factual - though maybe no 6 is an exaggeration). Once you pass no. 3 it becomes clear, that you leave a common sense interpretation of commerce and engage in "stretching".
In generally ascending order of breadth, various writers and Justices have defined “commerce” as:
1) The trafficking and trading of economic commodities
2) The trafficking and trading of economic commodities and the modes of their transportation
3)The trafficking and trading of any kind of commodity and the mode of its transportation
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4) The movement of any thing or any person and its mode of transportation
5) Economic activity that substantially or causally impacts on the trafficking, trading, or transportation of commodities
6) Any human activity or other phenomenon that has any ultimate impact on activities in more states than one.