By who's definition? Congress'? The President's? The USSC's? Your's?
What if the United States Supreme Court rules that a law is Constitutional? Does that make it valid? (Roe v. Wade)
What if a law is passed by Congress, but not challenged in the courts? Since the courts have not ruled on it's constitutionality, is the law valid? (Campaign Finance Reform)
What if the President vetoes a law passed by Congess because he says the law is unconstitutional, yet the Congress overrides the veto? Is that law valid?
If we, personally, don't feel that a law is constitutional, therefore invalid, may we disobey that law?
"It is certainly unfortunate that our national government leaders can not read the Constitution."
I think you mean, "It is certainly unfortunate that our national government leaders can not read the Constitution the way I do".
Actually yes, yes it does. Marbury v. Madison (1803, Chief Justice John Marshall presiding) It was this case wherein the Supreme Court established its powers of review over acts of congress and to determine the constitutionality of those acts.
I'd say the poster is making the same points contained in the Mission Statement of Free Republic:
"What is our mission? Free Republic is dedicated to reversing the trend of unconstitutional government expansion and is advocating a complete restoration of our constitutional republic."