In January 2001, the British Parliament passed a bill that authorized government funding for human embryonic stem cell research. Seven months later, in his first televised address to the nation, President George W. Bush pledged to do the opposite. By executive order, he denied federal funding for all research involving the creation of new human embryonic stem cell lines. Stem cell researchers who accepted federal dollars would be limited to working with a small number of officially recognized preexisting lines.

Bush made his decision for moral reasons: he wanted to discourage "further destruction of human embryos that have at least the potential for life." Regardless of whether the funding ban has accomplished that aim -- and critics believe it has had the opposite effect -- it has had a profound impact on a field that proponents believe holds the possibility of cures for Parkinson's disease, paralysis, diabetes, and a host of other ailments.