Ever since abortion was legalized by the Supreme Court in 1973 in its landmark decision Roe v. Wade, abortion opponents have tried to restrict the procedure or overturn the ruling. In the late 1990s, abortion opponents focused on the medical procedure known as intact dilation and extraction, more commonly called late-term or partial-birth abortion. The controversial procedure is used during the second or third trimester of a pregnancy and involves partially delivering the fetus in order to perform the abortion. Since 1995 opponents of late- term abortions have introduced bills in Congress to ban the procedure, but none has yet been passed into law.

Planned Parenthood and other pro-choice supporters contend that efforts to ban late-term abortions are thinly disguised attempts to ban abortion altogether. The legislation is so broad, its critics assert, that it could apply to abortion at any stage...