Wickard v. Filburn[1] effectively took nearly all of the constitutional scope limits off of the federal government. All the government needs to justify interference in the most mundane of human interactions is to find a broader economic nexus in the activity.
Summarized "The Court reasoned that Congress could regulate activity within a single state under the Commerce Clause, even if each individual activity had a trivial effect on interstate commerce, as long as the intrastate activity viewed in the aggregate would have a substantial effect on interstate commerce. To this extent, the opinion went against prior decisions that had analyzed whether an activity was local, or whether its effects were direct or indirect."[2]