In a letter to Treasury Secretary Henry Paulson earlier this month, four leading Democratic congressman urged action to pressure the Japanese to strengthen the value of the Japanese yen by selling off its reserves of dollars and euros. They noted that a weaker yen had artificially cheapened Japanese exports and they attributed the yen’s weakness to Japanese government policy.

There is nothing new about congressmen complaining about Asian currencies; complaints about the Chinese yuan have been a staple of recent years. But the complaints about the market-determined Japanese yen are different. There is no doubt that the Chinese currency is primarily set by the Chinese authorities. After all, they intervene in the foreign exchange market at the staggering rate of U.S. $250 billion a year to prevent their currency from appreciating.

In contrast, the Japanese yen floats freely in international currency markets in a manner that the U.S. government has urged on other Asian countries. Indeed, since March 2004, the Japanese authorities have totally refrained from any intervention, verbal or otherwise, in their foreign exchange market. Nor does the letter allege any. Instead, it argues that interventions earlier in the decade, along with Japanese monetary and fiscal policies, are leading to a depressed yen.

The congressmen want the Japanese to sell their currency reserves to drive up the value of the yen at the very time that they are urging China not to intervene in its foreign exchange market.

What makes the congressmen confident that the yen’s value is too low? They cite Japan’s success in exporting cars and trucks to the United States, as well as the bilateral trade deficit. They are presuming, without argument, that Japanese policy—rather than the relative attractiveness of Japanese versus American goods—is causing the imbalance.

This complaint about the yen is not about how the game is played, it’s about results. As in sports, it is far more reasonable to call for fair play than to call for good outcomes. What could we ask the Japanese to do? The congressmen want the Japanese to sell their currency reserves to drive up the value of the yen at the very time that they are urging China not to intervene in its foreign exchange market.

They are asking Japan to tighten its monetary policy to support the currency at a particularly bad time for the fragile Japanese economic recovery. Japan has not yet convincingly shaken off the deflation that has plagued it over the past decade. The world’s second-largest economy does not, and should not, artificially manipulate its currency to further the interests of the United States. Japanese regulators demonstrated their independence last week, when Japan did raise its interest rates and the yen failed to rally.

It is possible that the congressmen want to fix international exchange rates at government-determined levels. But that would require a return to a system of the sort that was abandoned several decades ago (commonly known as Bretton Woods). And that system is simply incompatible with the capital mobility that makes global markets so dynamic.

The U.S. approach to Japan affects the credibility of our approach to the vexing Chinese currency issue. U.S. policy has been to urge the Chinese toward a more market-determined yuan. An expression of dissatisfaction with market-determined rates in Japan would signal that U.S. currency demands are unreasonable and impossible ever to satisfy. That would be unlikely to further the legitimate U.S. and global interest in allowing necessary movements in the Chinese currency.