Although Congress as a whole has yet to act, a key congressional committee's vote to ban any secret aid for military operations inside Nicaragua may already have foreign policy implications.
Democrats who hold a majority in the influential House Select Committee on Intelligence ignored the objections of Republicans on the committee and voted Tuesday to ban all covert aid provided by the US Central Intelligence Agency (CIA) to military or paramilitary groups operating in Nicaragua.
The vote would not have any immediate effect on covert funding for insurgent groups fighting the Sandinista regime inside Nicaragua. But representatives from two such groups - one of which is reported to be receiving CIA aid and the other which says it is not - contend that the House vote will damage morale among the insurgents and send a signal to Central America that United States resolve is weakening.
The vote may also add to the strain in relations between the CIA and the House and Senate committees with which the agency shares intelligence data. The two committees don't have the power to veto secret CIA operations. But the law requires that they be informed about such operations, and the two committees do have a say over funding for the CIA.
The committee vote also could have an inhibiting effect on future CIA secret operations elsewhere in the world by serving as a warning that the intelligence committees have a limited tolerance for such activities. Even if the committee vote doesn't lead to a law banning secret operations in Nicaragua, it might at the least make the administration leery of trying to increase secret funds going to such operations.
Some Democratic proponents of the ban hope that their warning shot will be powerful enough to get President Reagan to withdraw support for the CIA's Nicaragua operations altogether. But that seems unlikely. Mr. Reagan called the committee's vote ''irresponsible'' and vowed to ''keep right on fighting'' against the measure.
But the impact of the House committee's move has been magnified by the fact that it is so unusual. The intelligence committees usually handle their objections to proposed CIA actions in secret. A Senate intelligence committee source said some months ago that the committee had been able to get the CIA to halt some questionable actions because of objections that senators raised in private.
In the case of Nicaragua, however, so much information about the CIA-backed operation was coming into the open from journalists on the scene that some House members felt obliged to speak out just on the basis of publicly available information. The administration was saying that it had no intention of using covert operations to overthrow the Sandinista regime, but some of the guerrilla leaders told journalists that regardless of what Washington was saying this was precisely their aim.
The vote marked the first time in seven years that Congress has openly considered banning a secret CIA operation. In late 1975 and early 1976, Congress voted to stop the CIA from supplying arms to insurgent groups fighting against the left-leaning government of Angola.
Democrats on the House intelligence committee argue that CIA aid to the guerrillas now fighting in the north of Nicaragua is illegal because it violates current restrictions against aid that might be aimed at overthrowing the government of Nicaragua.
But they also contend that the so-called secret war against Nicaragua could destabilize Honduras, strengthen the Marxist-Leninist elements within the Sandinista regime, increase the chances of war between Nicaragua and Honduras, and alienate key Latin American allies of the United States.
Some Democrats also argue that the guerrillas have failed to achieve the aim that President Reagan stated is the sole purpose of the CIA-backed operations: interdicting the flow of arms from Nicaragua to El Salvador.
On the MacNeil-Lehrer Report of May 3, Sen. Christopher Dodd (D) of Connecticut argued that if the administration could demonstrate that the CIA-backed guerrillas had captured arms on their way to El Salvador they would have displayed them by now. Sen. Malcolm Wallop (R) of Wyoming countered that the administration did have evidence that arms had been seized. Rep. C.W. Bill Young (R) of Florida said that the interdiction effort had not been as successful so far as the administration would like but that it had begun only a relatively short time ago.
Representative Young said the House committee vote would boost the morale of the Sandinista regime and discourage those who are allied with the US. Two representatives of groups now battling the Sandinistas - the CIA-backed Nicaraguan Democratic Force (FDN) and the Costa Rica-based Democratic Revolutionary Alliance (ARDE) -tended to agree with Young.
''One signal it sends to people who are fighting in Nicaragua is that they may not be able to trust the United States,'' said Alfonso Robelo Callejas, an ARDE representative now visiting Washington.