What is the “No Second Interference” rule in patent law?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The “No Second Interference” rule in patent law refers to the principle that there should not be a second interference proceeding between the same parties on patentably indistinct subject matter. This rule is outlined in MPEP 2308.03(c), which states:

“No second interference should occur between the same parties on patentably indistinct subject matter.”

This rule is designed to prevent redundant proceedings and ensure efficiency in the patent examination process.