Harsh language, the Reagan administration accuses the Mexican government of tolerating widespread drug trafficking and the pervasive corruption that it generates. This week the U.S. commissioner of customs, William von Raab, denounced "ingrained corruption in the Mexican law enforcement establishment." Assistant Secretary of State Elliott Abrams added that "they have got to get organized to stop this before it gets too late, and it can get too late." It's quite true that there's a heavy flow of drugs smuggled from Mexico into the United States, and it's also true that there is much corruption in Mexico related to the drug trade.

But you might also want to look at this corrosive and degrading trade from its other side.

The United States, a country with three times as many people as Mexico and 20 times its income, is the world's most voracious and lucrative market for illegal drugs. The enormous profits to be gained in the American drug market filter southward along the routes of supply on a scale that not only subverts individual policemen and politicians but also threatens the political system itself in some parts of the country. American officials, having failed repeatedly to control the demand for drugs here, now are railing against Mexico, far poorer and less well equipped, for its similar failure to control the supply.

A question: which country has the greater and more legitimate grievance against the other?

While Mexico has done less than Americans had hoped to choke off the movement of drugs northward, the Americans have been equally unsuccessful in reducing the movement of dollars southward -- dollars in the hands of professional smugglers playing for very high stakes in this ugliest and most destructive of businesses.

SK Political corruption is as deplorable in Mexico as in any country, and in Mexico that process has, as the Reagan administration argues, gone a long way. But the Mexican government and Mexican police are conducting a more vigorous, and far bloodier, war against it than you might have thought from the testimony at the Senate hearing at which Mr. von Raab and his colleagues were speaking. Dozens of Mexican police officers have lost their lives in the continuing struggle with the smugglers.

The destructiveness of the drug trade justifies using any strategy that promises even modest progress against it. But the unhappy reality is that, as long as the market within the United States operates on its present gigantic scale, any attempt to cut off the foreign sources of supply is likely to have, at best, very limited success