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In response to A:
That's Congress' job. To create and enact laws that have a broad usage of terms that are then decided by private bureaucracies. It's part of the Iron Triangle. Congress knows it won't be able to agree of the nuances of each bill, so they leave it vague and let the private bureaucracies fill in the blanks, sometimes government agencies (like the Environmental Protection Agency), to further the development of the law. Congress once made a law that, loosely, stated "and it may do anything that enables the general welfare of our society". Go into the dictionary and search for the rest of your life for words more vague and nondescript than "general" and "welfare". You won't ever find them. It was the Commerce clause that enabled the US Government to handle matters of interstate commerce.

However, not all bad comes from the Iron Triangle. From the Commerce clause came the Interstate Highway System - America's Autobahn. The government created the highway system so it could mediate the transportation of interstate goods and services, and look where it is now. It serves as one of the most highly used casual transportation arteries in the entire world. (Fun fact: for something like every 3 miles of interstate, there is at least 1 mile of straight interstate. For, in cases of national emergency, planes can use the interstate as a runway.)