Dr. Leroy Carhart, an abortion provider, filed a suit on behalf of himself and his patients, which challenged the statute's constitutionality.  The federal district court permanently enjoined the statute, and the court found the statute unconstitutional for several reasons.

1.  It banned the most common abortion procedure for second trimester pregnancies.
2.  It placed an undue burden on a woman by forcing her to chose a riskier second trimester procedure than the common D&X procedure in order to promote the well-being of non-viable fetuses.
3.  "The statute is unconstitutionally vague because the meaning of 'substantial portion' is unclear. (Carhart v. Stenberg, 11 F. Supp. 2d 1099).

  The state of Nebraska appealed the decision to the U.S. Circuit Court of Appeals for the Eighth Circuit, which affirmed the district court's decision.  The circuit court also found that the Nebraska statute was unconstitutional for making illegal the most common second term abortion, placing an undue burden on a woman's right to choose.

According to NARAL,

"The State of Nebraska appealed to the U.S. Supreme Court, and on January 14, 2000, the Supreme Court agreed to review the case. The Court will consider two questions: (1) whether the Eighth Circuit, in interpreting the Nebraska statute as banning more than one procedure, properly followed rules of statutory interpretation and gave due deference to state sovereignty and (2) whether the Nebraska statute is an unconstitutional "undue burden" on the right to choose abortion. A statute imposes an undue burden on the right to choose if the statute has the "purpose or effect of placing a substantial obstacle in the path of a woman seeking an abortion of a nonviable fetus." Planned Parenthood of Southeastern Pennsylvania v. Casey, 505 U.S. 833, 877 (1992)." 

    On June 28th, 2000, the Supreme Court, by a narrow 5-4 ruling, struck down Nebraska's ban on so-called partial-birth abortions.  It declared that the ban violated the U.S. constitution by failing to provide an exception for a woman's health and containing language that was overly broad and could lead to the banning of other more common abortion procedures.  This landmark decision was seen as a major victory for the pro-choice supporters, and for the pro-life, a devastating defeat.