I have supposed an opposition to be made to the right in Congress by the owner of the land and other individuals charged with breaches of laws made to protect the works from injury, because it is the mildest form in which it can present itself.  It is not, however, the only one.  A State, also, may contest the right, and then the controversy assumes another character.  Government might contend against government, for to a certain extent both the Governments are sovereign and independent of each other, and in that form it is possible, though not probable, that opposition might be made.  To each limitations are prescribed, and should a contest rise between them respecting their rights and the people sustain it with anything like an equal division of numbers the worst consequences might ensue.

It may be urged that the opposition suggested by the owner of the land or by the States individually may be avoided by a satisfactory arrangement with the parties.  But a suppression of opposition in that way is no proof of a right in Congress, nor could it, if confined to that limit, remove all the impediments to the exercise of the power.  It is not sufficient that Congress may by the command and application of the public revenue purchase the soil, and thus silence that class of individuals, or by the accommodation afforded to individual States put down opposition on their part.  Congress must be able rightfully to control all opposition or they can not carry the system into effect.  Cases would inevitably occur to put the right to the test.  The work must be preserved from injury, tolls must be collected, offenders must be punished.  With these culprits no bargain can be made.  When brought to trial they must deny the validity of the law, and that plea being sustained all claim to the right ceases.

If the United States possess this power, it must be either because it has been specifically granted or that it is incidental and necessary to carry into effect some specific grant.  The advocates for the power derive it from the following sources:  First, the right to establish post-offices and post-roads; second, to declare war; third, to regulate commerce among the several States; fourth, from the power to pay the debts and provide for the common defense and general welfare of the United States; fifth, from the power to make all laws necessary and proper for carrying into execution all the powers vested by the Constitution in the Government of the United States or in any department or officer thereof; sixth and lastly, from the power to dispose of and make all needful rules and regulations respecting the territory and other property of the United States.  It is to be observed that there is but little accord among the advocates for this power as to the particular source from whence it is derived.  They all agree, however, in ascribing it to some one or more of those above mentioned.  I will examine the ground of the claim in each instance.