THE MAJOR immigration reform bill now heading for House consideration before congressional adjournment still faces one last assault by opponents. It is on the question of amnesty for undocumented aliens already living in this country. This issue should not be allowed to cause the kind of confusion that will, in a situation where time is short, kill an important piece of legislation. Amnesty is a vital part of a delicately balanced compromise that has attracted support for this bill from a broad range of legislators. If it is eliminated, the compromise involving employer sanctions, strict enforcement, family and national preferences, foreign and economic policy, refugees and the lives of millions of individuals may unravel.

Almost everyone agree that people who have been in this country for many years, who have worked and contributed to our society, should not be summarily deported. The battling has been over what year should be the cutoff point. Opponents of a broad amnesty will agree to let everyone stay who has been here since l973. Others want to fold in everyone who is in the country on the date of enactment.

The compromise is in two parts: those who have been here since l976 can become permanent residents immediately; those who have been here since l979 may stay, but must wait three years before becoming permanent residents. That status is the first step toward citizenship and allows individuals not only to work but to petition to bring in certain family members. An additional special exception is made for Cubans and Haitians who arrived during the year l980, since many came at that time in response to President Carter's assurance that they would be admitted. Each petition for amnesty will be considered separately, and no one will be granted the privilege unless he meets the standards that apply to all immigrants. A criminal record, for example, a drug conviction or membership in the Communist or Nazi parties would disqualify an applicant. Finally, the compromise provides that none of these legalized aliens shall, for three years, be eligible for any federal assistance programs with the exception, in some cases though not all, of aid for the aged, blind, disabled or those experiencing medical emergencies. States may make similar exclusions.

The amnesty provision is not, as you can see, a mindless giveaway to undeserving lawbreakers, but a carefully crafted compromise between those who want to find and deport millions of aliens -- and who believe that can even be done -- and those who would adopt no limits at all. During many months of Senate and House committee consideration of the bill, the exact provisions have been adjusted, amended and generally fiddled with. The present compromise is a result that should be accepted by the House in the interest of passing a good bill in the short time available.