There is bittersweet news for lemon lovers.

First, the sweet. By order of the U.S. Department of Agriculture, California and Arizona growers will be allowed to ship 210,000 cartons of lemons (at 40 pounds apiece) to market this week.

The bitter side: For every lemon that makes it to market, three will be prohibited from going to market. That is because of government regulation.

It all has to do with federal marketing orders, one of the most controversial agricultural issues of the Reagan era. And the whole thing is cropping up again.

A few examples:

* Carl and Richard Pescosolido, California farmers who think they ought to be able to sell all the fruit they grow, are suing in federal court here to abolish the lemon-marketing order's weekly allocation provisions. They claim a "conspiracy" that reaches all the way to White House counselor Edwin Meese III.

* But farmers who like the idea of controlling the flow of produce are about to persuade Congress to bar the Office of Management and Budget from reviewing or commenting on the USDA's handling of 47 marketing orders.

* OMB Director David A. Stockman warned the House this month that he would recommend a presidential veto of such a prohibition. But the House went ahead last week and voted, 319 to 97, against removing the ban from a pending appropriations bill.

* The Senate may take up a similar measure this week, and another Stockman veto warning is expected. Senate aides aren't predicting how the debate will turn out.

By way of background, the marketing orders became controversial early in 1981, shortly after President Reagan put a task force to work reviewing federal regulations that were unnecessary or unpalatable to a politically conservative administration bent on turning free-market forces loose.

By coincidence, the controversy was spurred by front-page stories reporting the destruction of thousands of tons of California-grown navel oranges that couldn't be sold because of marketing orders.

Reagan's reviewers swallowed hard and recommended changes. Since then, the Justice Department, the Small Business Administration and the General Accounting Office have raised more questions about the legality of the marketing orders. But protected growers have been thumping the political drums to keep the marketing order program alive.

The orders date back to the New Deal era, when depressed farmers wanted some sort of tool to help prop up prices. The orders, now covering about three dozen commodities from lemons and milk to spearmint oil and celery, basically keep prices up by regulating supplies.

The orders are complex and vary in purpose from crop to crop. But Rep. George Miller (D-Calif.), a consumer advocate who is one of the House's tartest critics of marketing orders, has a simple way of explaining the system.

Last week he sent around paper bags, each containing 10 oranges. With each bag was a message explaining that four of the 10 oranges, 40 percent, could not go to U.S. consumers because of the marketing order. In the case of lemons, it will be about seven of every 10 this year.

"So much for the free-market system," Miller told the House. "This is price fixing. This is restraint of trade. And the agriculture community has gotten the government to go along with it . . . . The biggest insult is that out of the 83,000 tons of oranges that were fed to cattle last year, 72,000 of those tons were produced by federally subsidized water brought to you by the taxpayers, a result insulting to the people of this country."

But one farm-district legislator after another stood up in defense of the marketing orders, arguing that they are a gift from farmers to consumers by assuring reasonable prices and steady supplies of citrus fruit, milk, nuts and other basics covered by the orders.

By the same token, of course, consumers lose out when supplies are abundant because the market never gets saturated enough to force prices dramatically down.

Nevertheless, Miller and his small band of allies, in the ironic position of defending the regulatory review rights of their usual nemesis Stockman, didn't get to first base.

Rep. Barney Frank (D-Mass.), chief sponsor of the amendment Miller is pushing, had a last word: "I appreciate the fact that all these growers take time from their busy schedules of picking and planting and shaking and whatever, and they sit down and they have all these votes and they spend all this money just to benefit the consumers. It is an unparalleled example of beneficence."