THE CARTER administration's policy on drug abuses is beginning to take shape, and it appears to differ sharply from that of its predecessors regarding marijuana, though not with respect to heroin. Dr. Peter G. Bourne, the head of the administration's office ond drug-abuse policy, made it clear before a House committee that he thinks the criminal sanction may be the most serious consequence of smoking marijuana, a view that is consistent with the evidence from the laboratories and the prisons.

Heroin is the harder case. And even if this administration appears to be pursuing policies that have been tried before, it is worth taking a closer look at those policies to see whethe there may not be something about them that promises greater success. Heroin is na unusual item in commerce in at least one important respect: Once there is a supply, the chances are that it will create its own demand. Dr. Bourne, one of the world's leading authorities on the substance, is committed to th idea of destroying the supply sources for heroin. That approach has been tried by administrations in the past with mixed success. The Nixon administraion succeeded in persuading Turkey to get out of the opium business, only to find itself fighting a rear-guard action against Mexican heroin.

That experience has made some drug authorities wary of society's ability to succeed in the struggle against the supply. Instead, there has been more talk of heroin maintenance programs, somein imitation of the British system and some that would be "lures" intended to get people into treatment. Dr. Bourne's approach is to go forward on supply interdiction rathter than surrender on one front in the fight against heroin, as a maintenance program would appear to do.

Question: How can the Carter administration expect to succeed at supply interdiction if past governments have failed? There is some evidence of improved prospects for reducing the world supply. For one thing, Turkey has stayed out of the illicit opium business as far as can be determined. For another, the United States-assisted effort in Mexico has been showing some success. Overflights over Mexico's poppy field show that its crop eradication program is working to a substantial degree - or so government officials now believe. They concede that some poppy crops are being hidden among other crops, such as corn, but that still has not dampened the mild optimism of the adminstraion.

The next large question mark in the worldwide struggle with opium is the "Golden Triangle" of Southeast Asia. The poppy fields that produce opium that can turn up in Western markets from that region appear now to be under the control of the Burmese Communists, and Western anti-drug initiatives in that part of the world have been notably unsuccessful. Even so, the major problems once posed by Turkey and Mexico have lessened and the administration is hoping for some sort of breakthrough in Southeast Asia.

To add to the administration's hopes of progress at home, officials point to the fact that, in past, various aspects of the program have been scattered through the federal government in nearly a dozen different departments and agencies; now the President has given Dr. Bourne responsibility for the total governmental effort. That alone is one more reason to share the administration's cautious hopes for reducing heroin dependency in this country.