WASHINGTON - The Supreme Court on Monday scaled back a controversial legal test that has made it difficult to challenge patents on new products.

In a unanimous ruling, the justices said a federal appeals court had gone too far in embracing a standard that has fueled an era of patent protection.

The court said a federal appeals court applied the test in a manner that is too narrow and too rigid.

The case addresses one of the most basic issues in patent law: How to determine whether a product is obvious and therefore not worthy of a patent.

In the case of KSR International Co. v. Teleflex Inc., the U.S. Court of Appeals for the Federal Circuit upheld a patent for adjustable gas pedals. That court in Washington, D.C., hears all appeals in the field of patents.

The legal test at issue in the Teleflex lawsuit has been criticized by the Bush administration as leading to an unwarranted extension of patent protection to claimed inventions that are obvious. Critics of the test say it results in less competition and stifles innovation. Proponents warned that throwing out the standard would upset decades of settled law.

To invalidate a patent, a challenger must show that all parts of a claimed invention were known previously. In addition, the challenger must show that there is a prior "teaching, suggestion or motivation" to combine these prior technologies to produce the invention.

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