Let's look at the law. 35 U.S.C. § 121 states:
"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."
Despite what the law clearly says, the Manual of Patent Examining Procedure (Section 803) includes this rule instead:
"A]n application may properly be required to be restricted to one of two or more claimed inventions only if they are able to support separate patents and they are either independent or distinct."
and:
"There would be a serious burden on the examiner if restriction is not required."
Essentially, the law states the inventions must be independent and distinct, but the MPEP allows for restriction if the inventions are independent or distinct. The administrative rule employed by the U.S.P.T.O. can therefore be challenged as being outside the scope of the statute, but as of to date, it has not been.
"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."
Despite what the law clearly says, the Manual of Patent Examining Procedure (Section 803) includes this rule instead:
"A]n application may properly be required to be restricted to one of two or more claimed inventions only if they are able to support separate patents and they are either independent or distinct."
and:
"There would be a serious burden on the examiner if restriction is not required."
Essentially, the law states the inventions must be independent and distinct, but the MPEP allows for restriction if the inventions are independent or distinct. The administrative rule employed by the U.S.P.T.O. can therefore be challenged as being outside the scope of the statute, but as of to date, it has not been.