If two or more independent and distinct inventions are claimed in one application, the Director may require the application to be restricted to one of the inventions. If the other invention is made the subject of a divisional application which complies with the requirements of section 120 it shall be entitled to the benefit of the filing date of the original application. A patent issuing on an application with respect to which a requirement for restriction under this section has been made, or on an application filed as a result of such a requirement, shall not be used as a reference either in the Patent and Trademark Office or in the courts against a divisional application or against the original application or any patent issued on either of them, if the divisional application is filed before the issuance of the patent on the other application. The validity of a patent shall not be questioned for failure of the Director to require the application to be restricted to one invention.
35 U.S. Code § 121 - Divisional applications
This section enacts as law existing practice with respect to division, at the same time introducing a number of changes. Division is made discretionary with the Commissioner. The requirements of section 120 are made applicable and neither of the resulting patents can be held invalid over the other merely because of their being divided in several patents. In some cases a divisional application may be filed by the assignee.
2011—Pub. L. 112–29, § 20(j), struck out “of this title” after “120”.
Pub. L. 112–29, § 4(a)(2), struck out “If a divisional application is directed solely to subject matter described and claimed in the original application as filed, the Director may dispense with signing and execution by the inventor.” before “The validity of a patent”.
1975—Pub. L. 93–596 substituted “Patent and Trademark Office” for “Patent Office”.
Amendment by section 4(a)(2) of Pub. L. 112–29 effective upon the expiration of the 1-year period beginning on Sept. 16, 2011, and applicable to any patent application that is filed on or after that effective date, see section 4(e) of Pub. L. 112–29, set out as a note under section 111 of this title.
Amendment by section 20(j) of Pub. L. 112–29 effective upon the expiration of the 1-year period beginning on Sept. 16, 2011, and applicable to proceedings commenced on or after that effective date, see section 20(l) of Pub. L. 112–29, set out as a note under section 2 of this title.