Please note: The post contains numerous questions. The eNotes Homework Help policy allows for one question per post. This answer addresses Question 4.
The Commerce Clause is Article I, Section 8, Clause 3 of the US Constitution. It states that the US Congress shall have the power “to regulate commerce with foreign nations, and among the several states, and with the Indian Tribes.” Each of these may be considered a separate power granted to Congress. Its interpretation is significant within larger discussions of the relationship between the federal government and the states. Precisely what the regulatory power means has been the subject of ongoing debate. One key issue is the degree to which the legislative branch has power over activities performed by or within the states, including the residents and citizens thereof.
On a fundamental level, the definition of “commerce” itself is at the heart of different interpretations. “Commerce” in the late 18th century was more likely to mean social intercourse and commercial transactions. Over the centuries, the connotation of commerce changed to involve primarily economic effects, especially those that are “substantial.” The government began to consider more the cumulative effect on interstate commerce. A landmark U.S. Supreme Court decision for this interpretation was the 1937 NLRB (National Labor Relations Board) v. Jones. While some Supreme Court cases relying on this clause liberally interpreted the effects on commerce, the later 20th century tended towards a narrower the interpretation that stresses regulation of specifically commercial channels and instrumentalities.
The limits on state actions extends to their passage of laws concerning to activities that involve interstate commerce. The implications are especially crucial for business transactions. A common interpretation is that state governments cannot favor businesses that primarily or exclusively do business within that state (protectionism). An example of a case that drew on this clause is West Lynn Creamery v Healy (1994), regarding the state of Massachusetts’s ability to tax milk products, given that many were transported across state lines. A recent case dealing with crossing state lines involves marijuana, as it is legal is some states but not others.