To understand fully what is happening in Poland and how the United States might act to influence the situation, it is necessary to understand the meaning of ''martial law.''
Martial law is a well-established legal conception; it means the international law of war applies to the relations between a government and the people governed by that body of law. It is the body of law applied by an army of occupation or a national army during a civil war when the government considers all or part of the population has lost the ''habit of obedience'' (to use a technical phrase).
President Lincoln decreed martial law throughout the US during the American civil war. Although the Supreme Court held as a matter of American constitutional law that martial law could not be imposed by the executive branch except in the area of actual war and when the ordinary courts are closed, that decision was not until 1866.
The normal courts in Hawaii were closed by the governor from Dec. 7, 1941, until Oct. 24, 1944. The Supreme Court delayed until 1946 deciding that the suspension of the normal courts for some cases was unconstitutional, but in the meantime martial law had been applied and military tribunals had, without juries , decided cases involving civilian disobedience of military orders. Since the US did not declare war on Japan until Dec. 8, the day after martial law had been declared in Hawaii, it would be hard for the US to argue that martial law was not proper in extreme circumstances even without a formal state of war, or for a state to apply in its own territory even without a revolution or formal state of internal belligerency.
In Poland, where the US Constitution and its very special safeguards do not apply, the declaration of martial law would seem a serious but not inappropriate legal step in the delicate struggle for political power.
The legal effect of the declaration is to replace normal governance with military law. Under the international law of war, which is brought into play by a declaration of martial law, the military authorities do not have unlimited authority any more than the military authorities of a belligerent occupying army do. Just as the US has argued that Israel's rights of governance in the territories occupied by Israel in 1967 are restricted by provisions of the rules of land warfare and sup-plemented by the 1949 Geneva Conventions on the protection of civilian populations in time of war, even though there is no actual shooting in the area now, so Poland's rights in its own territory are limited by international humanitarian law.
Thus, while leaders of Solidarity can be detained for political reasons, as if prisoners of war, for the duration of ''active hostilities'' (presumably as long as the government of Poland considers Solidarity an active opposition party), they cannot be tried or executed except for violations of reasonable occupation decrees, such as curfew or public assembly regulations, ''war crimes'' or ''grave breaches'' of one of the treaties defining atrocities. It is doubtful leaders of Solidarity can be properly tried for ''treason'' or other political offenses against the Polish state under a regime of martial law.
There are many technical legal arguments that can be raised to cast doubt on some of these general assertions. But international support for them should be secure if they are argued properly. While the US is bound by general international law not to mix in the internal affairs of Poland, and by wise policy to remain neutral (whatever our poltical sympathies) in the struggle now being waged there, infractions of the laws of war by the ''occupying forces'' during a period of martial law are very serious.
There are forums like the League of International Red Cross Societies in which it is possible without abandoning neutrality or intervening in Polish internal affairs to raise legitimate questions and even to press for admission into Poland of neutral observers and possibly a ''protecting power'' to look after the interests of the world in the observance of the laws of war. Some of these pressures have in fact been brought to bear on Israel, and it will be a sign of the competence of American and other statesmen whether they are able to use the powerful tools of the law to influence events in Poland in ways more subtle and effective than embargoes and bluster can.
In sum, the response of the Polish government to the political challenge of Solidarity has been to shift the legal framework. That shift shows the concern of the Polish government for legal forms and, while it permits the government a wider scope for action against the leadership of Solidarity, it also permits a degree of American and other foreign influence in Poland that was not legally possible before. Failure of the US to use this opportunity would be tragic for Poland and for US influence and stature.