The Supreme Court on Monday agreed to answer a crucial question that arises in virtually every patent application: When is an invention so obvious that it does not deserve a patent?

The question is posed in KSR International v. Teleflex, which could produce “the most important patent ruling in a decade,” said Michael Barclay, a patent specialist at Wilson Sonsini Goodrich & Rosati. “I can hardly think of a patent case I’ve handled in 25 years where obviousness isn’t an issue.”