Oliver Wendell Holmes, Jr., Erie Company v. Board of Public Utility Com'rs…
“ That is one of the most obvious cases of the police power, or to put the same proposition in another form, the authority of the railroads to project their moving masses across thoroughfares must be taken to be subject to the implied limitation that it may be cut down whenever and so far as the safety of the public requires. It is said that if the same requirement were made for the other grade crossings of the road it would soon be bankrupt. That the States might be so foolish as to kill a goose that lays golden eggs for them, has no bearing on their constitutional rights. ”
