A change in the standard would "marginalize" the USPTO, Waxman argued. Congress is currently working on legislation that would allow new ways to challenge patents, he noted.
"Congress is on the job," he said.
The U.S. Department of Justice also argued against Microsoft. The current standard is "part and parcel" of patent law, said Malcolm Stewart, deputy solicitor general at the DOJ.
Representatives of both Microsoft and i4i said they were encouraged by Monday's arguments before the Supreme Court.
A decision for the lesser standard would be "devastating" to inventors, said Loudon Owen, i4i's chairman. The case will determine "whether or not innovation will be able to continue to exist on the pace and scale that it has to date," he said. "What Microsoft is looking to do is completely disrupt the patent system we have today."
Microsoft's assertions that i4i included the XML editor in a product before applying for the patent and that it destroyed source code are "utter nonsense," Owen added.
The case will have a huge impact on the U.S. economy, said Brad Smith, Microsoft's general counsel. The economy "depends on having a healthy patent system," he said. "A healthy patent system requires that we both have the ability to protect patents that deserve protections and that we have the ability to weed out those that do not."
Smith discounted the i4i argument that a new standard for invalidating patents would hurt innovation. Microsoft is one of the largest patent holders in the U.S., he said.
"If we're prepared to stand here and ... defend our patents under a preponderance-of-evidence standard, then anyone should be able to do the same thing," Smith said. "We have as strong an interest in a strong patent system as anybody."
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