What does 35 U.S.C. 121 say about patent validity and restriction requirements?

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Source: FAQ (MPEP-Based) BlueIron Update: 2024-09-27 10 Rules 4 Related FAQs 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. 35 U.S.C. 121 includes a crucial provision regarding patent validity and restriction requirements. As quoted in MPEP 805 : “the validity of a patent shall not be questioned for failure of the Director to require the application to be restricted to one invention.” This means that even if the USPTO did not require an applicant to separate multiple inventions into different applications, the resulting patent cannot be challenged on this basis alone. This provision protects patentees from post-grant challenges based on the USPTO’s administrative decisions during examination. Related Rules from the Manual of Patent Examining Procedure 10 rules Collapse Patent Validity Not Questioned for Improper Joinder MPEP 805 Prohibited Patent Validity Not Questioned for Improper Joinder of Inventions MPEP 805 Permitted Patent Validity Not Questioned for Unrestricted Applications MPEP 802 Prohibited Patent Validity Not Questioned for Unrestricted Applications MPEP 804 Prohibited Patent Validity Not Questioned for Unrestricted Applications MPEP 802 Prohibited Combining Multiple Inventions into One Application MPEP 803.03 Invention Restriction Requirement MPEP 802.01 Prohibited Form Paragraphs for Restriction Requirement MPEP 1504.05 Permitted Restriction Requirement for Interfering Claims MPEP 2303 Permitted Restriction Requirement When Unpatentable Claims Delay Interference MPEP 2303 Permitted Other Related FAQs 4 FAQs Collapse What protection does 35 U.S.C. 121 provide to patent holders regarding improper joinder? What is the effect of improper joinder on patent validity? How does MPEP 805 interpret the last sentence of 35 U.S.C. 121? Can a patent be invalidated for containing multiple inventions?