This is HUGE, because it re-introduces the notion of States' Rights in its proper context. For far too long, the Federal Government has wielded the Supremacy Clause as a bludgeon over States despite there being no explicit authority in the Constitution for many of their actions. This is also a huge ruling because it sets forth the principle that the Courts should not be the ultimate arbiter of laws but rather that the individual legislatures (both State and Federal) should take responsibility for more law-making.