The Constitution recognizes the legislative power of the States; and a law so enacted may impair the privileges of the Union, in which case a collision in unavoidable between that body and the State which has passed the law: and it only remains to select the least dangerous remedy, which is very clearly deducible from the general principles I have before established.

*k [Footnote k: See Chapter VI.

on "Judicial Power in America."] It may be conceived that, in the case under consideration, the Union might have used the State before a Federal court, which would have annulled the act, and by this means it would have adopted a natural course of proceeding; but the judicial power would have been placed in open hostility to the State, and it was desirable to avoid this predicament as much as possible.

The Americans hold that it is nearly impossible that a new law should not impair the interests of some private individual by its provisions: these private interests are assumed by the American legislators as the ground of attack against such measures as may be prejudicial to the Union, and it is to these cases that the protection of the Supreme Court is extended.
Suppose a State vends a certain portion of its territory to a company, and that a year afterwards it passes a law by which the territory is otherwise disposed of, and that clause of the Constitution which prohibits laws impairing the obligation of contracts violated.

When the purchaser under the second act appears to take possession, the possessor under the first act brings his action before the tribunals of the Union, and causes the title of the claimant to be pronounced null and void.