SO FAR, the trade bill is moving along pretty well in its perilous passage through the Senate. In the first of the crucial votes, last week the senators cut the energy security -- that is, oil protection -- section out of it. If that one had gone the other way, it might have meant the collapse of the bill itself. The oil section was an enormous concession to one special interest, the domestic oil producers, and if they had won it would have been impossible to keep out all the others. But the vote went the right way by a reassuringly substantial margin, maintaining the agreement that has been keeping the single-industry goodies and giveaways out of this legislation.

The next major vote will probably be on the provision requiring a company to give 90 days' notification of the closing of a plant employing 100 or more people. The case for it is that it can ease the blow to those people, providing time for counselling and planning for retraining and the transition to other work. Where employers provide advance notice, its supporters argue, unemployment and the disruption of people's lives is reduced. The authors have limited it to closings big enough to have an impact not only on individual workers but on whole towns.

To attempt to meet businesses' objections, the draftsmen have offered a series of exceptions. Notification would not be required when a plant closed for genuinely unforeseen reasons -- for example, a sudden loss of a contract. A company in trouble would not have to notify if it was trying to keep the operation going and feared that a closing announcement would destroy its credit. Temporary layoffs are not covered.

But most businesses don't like the idea on principle. They fear that this kind of requirement will contribute to the rigidity of industry, in the European manner, leaving them less agile to meet change. Expanding trade means change on a very serious scale, and most of this bill has to do with setting the rules for change in industrial patterns -- which means the way people earn their livings.

It's useful to make a distinction between the kind of legislation that provides a shock-absorber, and the kind that tries to prevent competitive shocks altogether by penalizing foreign goods and keeping them out of the country. The plant-closing provision is a shock absorber, an attempt to mitigate the most painful side-effects of competition and economic growth. It's not essential to this bill. But something like it may prove to be essential, sooner or later, to keep American markets open to expanding trade from abroad