SENATORS UNDOUBTEDLY thought they had an easy vote last week. Employers have been complaining that they do not fully understand the new immigration law, which prohibits them from hiring illegal aliens. Business lobbies claimed that their members would be penalized for inadvertent violations because, in the months since passage of the bill, there has not been sufficient time to understand its implications. So they persuaded lawmakers to extend the public information period another four months, thus postponing implementation of the first stage of employer sanctions, which were due to go into effect June 1. Instead of doing a favor for the businessmen, however, senators have simply created a muddle.

The Senate action came in the form of an amendment to the supplemental appropriations bill, which is still tied up in procedural knots and may never become law. Any employer who thinks an extension has been granted is mistaken. There was very little chance from the beginning that the amendment would be adopted by both houses and signed into law before June 1, but the hoopla surrounding the Senate vote has quite probably caused confusion.

The amendment was never necessary in the first place. The new immigration law already provides for a year-long transition period with no penalties for violations other than a warning. The Immigration and Naturalization Service, in addition, has agreed not even to issue warnings when a violation has occurred because of a misunderstanding of the law. This fact was emphasized by opponents of the amendment during debate and was cited in a letter that went to all senators from Sens. Simpson and Kennedy, who lead the immigration subcommittee. But it did not seem to sink in.

The reform measure was debated over a six-year period and was the result of arduously arrived-at compromises. It has already had an impact. Border apprehensions are down as much as 40 percent in some locations, according to Sen. Simpson, and that is because the certainty of employer sanctions has dried up the job market for undocumented workers. Fiddling with effective dates creates an uncertainty outside our borders and leads to doubts about this country's determination to implement sanctions at all. It also sends out a signal that other dates in the new law are negotiable -- that there is no need, for example, to apply for amnesty because it will surely be extended beyond its original one-year limit. It is a terrible disservice for senators to create the impression that this law is still being negotiated.