The sea is not a battlefield without rules

CNBC reports that Ukraine has intensified drone attacks on tankers operating near Crimea, as part of a deliberate strategy to cut off fuel supplies and transportation routes into Russian-held territory. I choose to engage this story not because I can judge the satellite guidance or the engineering of the weapons, but because the shape of the question is ancient and the principles at stake have not changed since nations first agreed that even war must have boundaries.

The lawfulness of the target matters before the strike, not after.

A tanker carrying fuel is not, on its face, a warship. Whether it becomes a lawful military objective depends on whether it is making what lawyers of my era called a direct contribution to hostilities — and what modern law of armed conflict calls a military objective of sufficient advantage to justify the loss. CNBC identifies these vessels as supplying Russian military operations; if that characterization is accurate and provable, the analysis shifts. If the vessels are commercially chartered, flagged in third countries, and carrying goods for civilian consumption, the analysis shifts the other way, and sharply. I cannot resolve that factual dispute from a news lead. I can say that the resolution of it is not optional.

Third-party flags carry third-party obligations — and third-party rights.

In my era, the great quarrel between maritime powers was precisely this: when a belligerent nation struck neutral shipping, it did not merely injure a shipowner. It injured the flag state. It strained every treaty that promised free navigation. The Jay Treaty of 1794 — in which I had a direct hand — was born partly from Britain's habit of seizing American vessels it deemed to be supplying its enemies. We insisted then, as principle demands now, that neutral cargo deserves neutral protection unless contraband can be specifically proven. If any of the tankers Ukraine has struck fly the flags of states not party to this conflict, those states have standing to protest, and their protest deserves a serious legal answer, not a diplomatic shrug.

A blockade, to be lawful, must be declared, effective, and impartially applied.

What Ukraine appears to be conducting — inference on my part, not reported fact — is something close to a de facto blockade of Crimean waters. The law of naval blockade, developed over centuries precisely to prevent the chaos of unchecked maritime warfare, requires that a blockade be formally declared, actually enforced across the relevant area, and applied without discrimination to vessels of all nations. A campaign of drone strikes that functions as a blockade without satisfying these conditions risks placing Ukraine outside the protections that international law would otherwise afford it. That matters strategically, not only morally: a party that cannot claim legal high ground invites reciprocal disregard for the rules it will one day need to invoke on its own behalf.

The precedent accumulates whether we intend it or not.

I spent much of my public life arguing that the United States could not afford to treat treaties as convenient when useful and ignorable when burdensome. The same logic applies here, and to every party observing this conflict. Each strike on a vessel without clear legal foundation, each failure to account for third-party flag rights, each unanswered claim of neutral injury — these accumulate into a body of practice that weakens the architecture of maritime law for everyone. Ukraine has legitimate grievances and legitimate military needs. Those do not dissolve the obligation to act within the law; they make it more urgent to do so, because a Ukraine that wins by eroding international law inherits a more dangerous world.

What should be done. Ukraine's allies — particularly those with experienced admiralty legal capacity — should publicly articulate the legal basis for each category of vessel targeted, distinguish military supply ships from commercial tankers, and engage any flag state whose vessels have been struck. If a de facto blockade is the strategy, it should be declared as such and administered according to established rules. The goal is to deprive Russia of fuel, not to deprive the world of the principle that the sea has law.