NIGERIA NOW THREATENS to cut oil shipments if the United States should disobediently recognize the newly elected government of Zimbabwe Rhodesia. Nigeria has already expanded its boycott of Israel and South Africa by closing its ports to tankers that have recently been to either of those countries. That amounts to a secondary boycott and, under American law, any company taking Nigerian oil under those circumstances commits a crime. Nigeria is challenging the United States either to ignore its own law or to do without more than a million barrels a day of Nigerian oil.

The U.S. government has managed to give the world the impression that it is frantic for oil to placate American motorists, who don't like waiting in line for gasoline. Nigeria is experimenting to see how much leverage a million barrrels a day can exert. It is invoking the oil weapon - the manipulation of oil exports to serve unrelated political purposes.

The conventional wisdom has held that only Saudi Arabia could credibly use the oil weapon. The Saudis are, in fact, using it currently. They are holding their production a bit low to indicate to an otherwise inattentive audience their displeasure with the Camp David agreements between Israel and Egypt. But the Saudis are cautious, the conventional wisdom argues, and do not wish to disrupt the world financial markets in which they now have very large interests.

Nigeria, in contrast, is not a notably plausible wielder of the oil weapon. To pay for the development of a large and heavily populated country, its government spends every dime of the oil revenues as fast as it arrives. Unlike Saudi Arabia, Nigeria cannot afford to forego potential oil earnings. But it assumes that the United States will simply cave in to its demands. The American performance this spring gives Nigerians some reason to think so.

Suppose for a moment that the Carter administration decided to protect the integrity of American foreign policy by ignoring the Nigerian threats. What would happen? If Nigeria cut this country off, much of the oil would doubtless find ready buyers in Europe where customers are anxious to build up stocks. But what would happen if all the major industrial countries together decided to protect their common interests by cutting back on oil consumption? They have made a rather imprecise agreement to cut back by the end of the year. But suppose, instead, they did it right now and created slack in the market. The sellers of oil would no longer be able to play one buyer off against another. The sellers could no longer assume that their customers were ready to make any humilating concession in order to get oil.

As unlikely as it now may seem, that is the kind of decisive action by the industrial nations that would make sense.