In a revealing interview with Tucker Carlson, President Donald Trump seemed to agree with his host's assessment that it would not be worth American blood or treasure to defend the newest member of the North Atlantic Treaty Organization (NATO), Montenegro, should that tiny Balkan country find itself at odds with its neighbors. There has already been a great deal written about the implications of these comments for European regional security, but I wanted to also bring in the ethical dimensions of the question and how this speaks to the continuing debate over American engagement.
Carlson's and Trump's comments reflect the transactional view of foreign policy that they hold: where the assessment of the worth of foreign policy is found in the balance sheet. Montenegro, in this view, is not going to be much of a security contributor because of its small size and lack of capabilities as well as the lack of geostrategic importance of its real estate (NATO gained nothing new in terms of its position in the Adriatic by adding Montenegro as a member). On the other hand, Montenegro could be a net security consumer if one assumes that Montenegro wants to leverage its NATO membership in its relationship with Serbia, its former partner in Yugoslavia and the successor "federal state."
However, Montenegro, in joining NATO, did not "sneak in": its membership had to be ratified by all existing alliance members. For the United States, this means that the U.S. Senate, exercising the treaty power as defined in Article II, Section 2, Clause 2 of the U.S. Constitution, had to vote to extend the guarantees of the Washington Treaty to Montenegro, which it did in March 2017 by a vote of 97-2. Two U.S. Senators–Rand Paul and Mike Lee–made the argument that it was not in U.S. interests to extend NATO membership to Montenegro–but were outvoted by their colleagues. Having made the promise, therefore, the ethical principle of pacta sunt servanda–"agreements must be kept"–should apply. If Montenegro has done nothing to void its NATO membership by failing to meet its obligations, then it should have no doubt that the U.S. will honor its commitment. It bears repeating that NATO members do have obligations to the alliance–and that the whole system of collective defense and burden sharing rests on the assumption that, having signed on the dotted line, all alliance members can, in turn, have absolute confidence that the alliance guarantees are intact.
Of course, what the Montenegro test reveals is a more underlying problem: that the U.S. has extended promises and guarantees without necessarily thinking through the consequences. As with previous rounds of NATO enlargement, the Senate debate was relatively pro forma, because there was a sense that guarantees could be extended at little or no cost. But this is a failing in and of itself, because serious obligations taken without an assessment of risks and costs cheapen those assurances. And this opens up a more long-term destabilizing possibility–that we cannot rely on agreements and commitments. After all, the counterpoint to pacta sunt servanda is the aphorism, “Parchment burns in fire.”