Kagan, as a Supreme Court justice, will be required to rule frequently on possible applications of Shariah law in the United States. She has already noted that she welcomes "good ideas wherever they originate" and is open to applications of foreign law to the interpretation of U.S. statutes and common law. In fact, a lawsuit seeking to ban Shariah Compliance Funds in banks that accepted TARP money (as violating the First Amendment separation of church and state) is now making its way up to the Supreme Court. Kagan cannot be trusted to rule dispassionately on this case, nor can we rely on her to exclude Shariah law from American jurisprudence.
For this reason -- if for no other -- senators should vote no on her confirmation.