The Supreme Court declined yesterday to hear a challenge to New Jersey's blue law, leaving some retailers without guidance as to whether they may face prosecution if they sell a wide array of items on Sundays.

One such item is sneakers. Are they clothing, a no-no under the law? asked Two Guys From Harrision Inc., a discount department store chain. Or are sneakers sporting goods, which can be sold legally?

Another such item is a hair-curler. Is it an appliance (sale forbidden) or a beauty aid (sale allowed)?

And a car stereo: Is it a piece of audio equipment (forbidden) or an automotive accessory (allowed)?

Actually, such questions aren't a problem statewide in New Jersey because the law, enacted in 1959, has a unique "local option" under which it is in effect only in the 10 (of 21) counties that adopted it in referendum elections.

The law bars Sunday retail sales of clothing and apparel, building and lumber supply materials, furniture, home and office furnishings, and appliances for homes or businesses.

Of the 27 Two Guys' outlets in New Jersey, 20 are in counties that adopted the law. To comply, the affected stores roped off certain departments. But in December 1975, the management defied the law by removing the ropes to permit sale on Sunday of everything sold Monday through Saturday.

As a result, six communities started criminal prosecutions. Two Guys' owner, Vornado Inc., then contended that the law was not only unconstitutionally vegue, (because, for example, it doesn't tell a merchant if he can sell items such as sneakers), but also that it denied the equal protection of laws guaranteed by the Constitution.

Although Vornado won a trial, a divided state supreme court upheld the law last June. Yesterday the U.S. Supreme Court let the ruling stand, along with a ruling upholding a Texas version. Previously, challenges to such laws in Maryland and Pennsylvania failed in the high court.

In Trenton, the New Jersey high tribunal held 5 to 2 that it is the function of lawmakers, not judges, to strike the balance between expected benefits to the public, such as protecting the ambience of Sunday as a day of rest, against expected detriments to would-be Sunday shoppers and merchants.

"Only if the anticipated benefits could be affirmatively established to be so illusory as to stamp the legislative classification [of saleable and nonsaleable goods] as arbitrary or capricious would a court be justified in striking it as lacking in equal protection or due process," the majority opinion said.

One dissenter, Justice Morris Pashman, wrote that the classification "fails abysmally when subjected to scrutiny under a standard too frequently ignored by judges attracted by the intellectual allure of legal niceties incomprehensible to the public - the test of common sense."

Another dissenter pointed out that a major objective of the legislature in passing the law was to give the "vast majority" of New Jersey residents repite from the daily routine. But there's as much hustle and bustle on Sundays as there ever was, he said.