THAT SWARM of loose papers you saw blowing around Lafayette Square the other day might have been the final report of the Select Commission on Immigration and Refugee Policy. This is the group, dominated by legislators of both parties, that spent two years pondering the United States' immigration and refugee policies, especially the problem of illegal immigration. Its principal recommendations in this area -- amnesty for old illegals and tighter controls on new ones -- were what President Reagan appeared to sweep into the park in his interview with Walter Cronkite Tuesday night.

Mr. Reagan was obviously ready for a question on the new report. In a truly flabbergasting way, he brushed past its recommendations and pronounced himself "very intrigued" by a suggestion from elsewhere to end the flow of "what we're calling illegal immigrants" by declaring the flow legal, creating "open borders" and granting visas to those who now cross on the sly. Mexico needs the "safety valve," he said, and the stability of this friendly state is in the American interest. If the flow were legalized, employers could no longer exploit illegals by threatening deportation, and taxes could be collected, too.

Mr. Reagan did not dot every i, and it is premature to say he has rejected or perhaps even considered the basic bargain -- close the back door, open a bit the front door -- the select commission proposed. What he said, however, is consistent with his past favor for temporary workers. Temporary-worker programs go to the key economic issue of how immigrants affect the American economy and particular groups within it. Employers, especially in border states, traditionally argue that native workers are unavailable for the particular jobs. Organized labor and other opponents see the same programs as competitive on the one hand and exploitative and tension-building on the other: that's why the bracero program, which brought in up to half-a-million Mexicans a year for 22 years, was ended in 1964. The commission, containing representatives of both schools, ducked and said that the current small-scale temporary program (30,000 workers) could be run better and perhaps expanded, but only "slightly."

Demonstrably, it is not now possible to establish, to the satisfaction of a legislature necessarily representing different interest groups, whether temporary workers are good or bad. So it makes sense to put off the issue until the country has tested tighter controls on illegal immigration, as the commission urges. But that is precisely the view President Reagan swept past on Tuesday. Did he really mean to? Is he not prepared to review, in the light of his national responsibilities, a position that was plainly formed in a California context? Of the many questions posed by immigration, that's one of the first.