Please learn what you are talking about before you go spouting nonsense. This is the LAW, it is entitled Sec. 922. - Unlawful acts and maybe found here
http://www4.law.cornell.edu/uscode/18/922.html
(d)
It shall be unlawful for any person to sell or otherwise dispose of any firearm or ammunition to any person knowing or having reasonable cause to believe that such person -
(1)
is under indictment for, or has been convicted in any court of, a crime punishable by imprisonment for a term exceeding one year;
(2)
is a fugitive from justice;
(3)
is an unlawful user of or addicted to any controlled substance (as defined in section 102 of the Controlled Substances Act (21 U.S.C. 802));
(4)
has been adjudicated as a mental defective or has been committed to any mental institution;
Everything in that post is correct.
Please learn to read a history book before you go spouting nonsense. The LAW has violated the Constitution innumerable times.
Remember checks and balances? The courts have found many, many laws to be oppressive, unfair, unConstitutional, and just plain stupid.