Not only is henna (Lawsonia Inermis) NOT causing "black henna" injuries, and permitted by FDA regulation as hair colorant, henna is part of the religious practice of many citizens of the United States.

The 1st Amendment of the US Constitution protects the rights of citizens to practice customs in accordance with their religion. Henna is associated with the practice of several religions. Blocking importation of, or banning henna use, conflicts with the Constitution of the United States of America.

A devout Muslim who has made his pilgrimage to Mecca is permitted to dye his beard with henna, to honor the Prophet Mohammed, who also dyed his beard with henna. Henna (Lawsonia Inermis) should be a permitted import for these men who wish to express their piety and devotion to their religion.
For references to the Muslim use of henna, see: http://www.islamicvoice.com/november.99/tibb.htm#HEN

Henna (Lawsonia Inermis) is also the only color an Orthodox Jewish woman or a conservative Muslim woman may use on her fingernails. No other nail polish is permitted, as their religion declares that with those paints, the fingernails cannot be properly cleaned before prayer. 100% pure henna must be allowed for these women, so they can pray.

Devotees of Hinduism feel that offerings are most acceptable to their deities when presented by hennaed hands. Henna should be allowed to pious Hindus who feel that their prayers and offerings may be shunned for lack of henna.

Women from all of the countries in North Africa, the Middle East, and South Asia have "The Night of the Henna" traditions as part of their weddings. The wedding tradition of hennaeing a woman's hands dates to 7000 BCE. A government official's misinformed and poorly reasoned ruling should NOT interrupt a beloved ritual that has endured for 9000 years and stretched over 60 countries! Jews adopted "The Night of the Henna" as a part of their wedding around 1000 BCE, and Sephardic Jews continue this to this day. Armenian Christians, and Coptic Christians also celebrate "The Night of the Henna". The Prophet Mohammed's own mother was hennaed at her wedding, and "The Night of the Henna" is one of the most important nights in any Muslim woman's life! For the Hindu, "The Night of the Henna" is a spectacular family party, the night every girl dreams of, when she will look like, and be treated as, a princess!
Some of these "Night of the Henna" traditions are described at:
http://www.veleisures.com/matrimonials/HinduWedding.asp
http://www.veleisures.com/matrimonials/SikhWedding.asp
http://www.veleisures.com/matrimonials/MuslimWedding.asp
http://www.sfusd.k12.ca.us/schwww/sch618/islam/
nbLinks/Islam_Women_Marriage.html

Hindu, Muslim, Sephardic Jewish, Rom, B'hai, Parsee, Zoasterian, Sikh, Coptic Christian, and Armenian Christian brides all celebrate "The Night of the Henna" before their weddings. These religions make up, at last census, 10,000,000 citizens of the USA. It would be tragic, as well as unconstitutional, to prevent these people's joy in celebrating and preserving their wedding traditions!
The census figures on USA citizens who have henna traditions are at:
http://www.adherents.com/rel_USA.html
http://www.religioustolerance.org/us_rel.htm

Brides who feel henna is a part of their religious, social, and ethnic traditions MUST be allowed to use henna. The 1st Amendment of the US Constitution protects the rights of citizens to practice customs in accordance with their religion.