The William Bagaley was a case heard by the United States Supreme Court in 1866. The case involved an appeal from the Circuit Court of the United States for the District of Columbia, which had ruled that a certain vessel and cargo were subject to forfeiture under federal law. At issue was whether or not Congress had authority to pass laws regulating commerce on navigable waters within state boundaries. The court held that Congress did have such authority, as it is granted power over interstate commerce through its enumerated powers in Article I Section 8 of the Constitution. Furthermore, they found that this particular act fell within those powers because it regulated navigation on navigable waters between states and with foreign countries; thus making it valid legislation under Congressional authority. As such, they affirmed the decision of lower courts ruling for forfeiture against William Bagaley's vessel and cargo.

In the case of The William Bagaley, the Supreme Court was asked to decide whether a vessel that had been sold in foreign waters could be seized and forfeited for violation of US customs laws. A majority opinion held that it could not, as such an act would violate international law. However, Justice Field dissented from this decision on two grounds: firstly, he argued that there was no clear evidence in support of the claim that seizing vessels abroad violated international law; secondly, he maintained that even if such a practice did conflict with international law principles, Congress still had authority under its constitutional powers to pass legislation allowing for forfeiture regardless. In conclusion then Justice Field believed that Congress should have been allowed to exercise its power over matters concerning foreign commerce and thus allow for seizure and forfeiture when necessary.