Rule:  If the legislation is not prohibited and is calculated to effect any of the objectives entrusted to the government, the Court should not question the necessity of the law. (judicial restraint)

The Fed law is the supreme law of the land.  Where Congress has been given the power to create (as here decided) a State cannot be given the power to destroy (by taxing).

Rule:  States cannot tax Fed entities. The courts will not strike down a congressional action so long as Congress has employed a means which is not prohibited by the Constitution and which rationally related to objectives that are themselves w/in constitutionally-enumerated powers.
-    Power of Fed. govt enumerates from people, not states.
-    concluded that a particular power could be implied from the explicit grant of others.
-    Court looked at Art I §8: power of the purse—raise revenue, taxes. Regulate commerce etc. along with necessary & proper clause (sec.5) which allows all regulation to achieve the powers enumerated.
-    “necessary” in the clause does not mean absolutely necessary but rather a broad definition: rationally related. Supported by examples: Fed prohibition on mail theft is not indispensable to the establishment of post offices & post roads.
-    NP clause is listed in the powers enumerated, not the limitations therefore intended to expand not limit powers.