John Hessin Clarke,
Great Northern Railway Company v…
“ It is also settled that a case, arising under the laws of the United States, nonremovable on the complaint, when commenced, cannot be converted into a removable one by evidence of the defendant or by an order of the court upon any issue tried upon the merits, but that suc conversion can only be accomplished by the voluntary amendment of his pleadings by the plaintiff or, where the case is not removable because of joinder of defendants, by the voluntary dismissal or nonsuit by him of a party or of parties defendant. ”
