“ We hold that petitioner's right to bring the suit in any eligible forum is a right of sufficient substantiality to be included within the Congressional mandate of § 5 of the Liability Act: 'Any contract, rule, regulation, or device whatsoever, the purpose or intent of which shall be to enable any common carrier to exempt itself from any liability created by this Act, shall to that extent be void * * *.' The contract before us is therefore void. ”

“ On each of these occasions petitioner signed an agreement stipulating that if his claim could not be settled and he elected to sue, 'such suit shall be commenced within the county or district where I resided at the time my injuries were sustained, or in the county or district where my injuries were sustained and not elsewhere.' [2] Although this provision defined the available forum as either the Circuit Court of Calhoun County, Michigan, or the United States District Court for the Eastern District of Michigan, petitioner brought an action in the Superior Court of Cook County, Illinois. ”

“ Section 6 of the Liability Act provides that 'Under this Act an action may be brought in a district court of the United States, in the district of the residence of the defendant, or in which the cause of action arose, or in which the defendant shall be doing business at the time of commercing such action. ”