Is it legal to poke fun at public figures? We are coming to the libel trial involving the Rev. Jerry Falwell against Larry Flynt, publisher of a soft-porn magazine, in a minute; but first the great cosmic issue:

Can you legally say President Reagan is a tadpole? A toad? A man of defective synapses? Surely there is no argument there. You can.

Can you say the president gets kickbacks from weapons manufacturers? Certainly not, unless you have a good basis for saying it.

The tadpole-toad charges will not be believed by anybody. The kickback charges, on the other hand, are very serious, might be believed and would certainly damage any president's reputation. If such charges were made I do not think a president could let them go unanswered, and if the charges were recklessly false, the person making the charges should have to pay a heavy price.

The Falwell case concerns a full-page parody ad for booze in Hustler, in which Falwell in effect endorses heavy drinking and says he "always gets sloshed" before preaching. The ad, identified as a parody or joke at the bottom, also suggested worse things. Falwell claims the magazine and its publisher have a history of malice towards him, and says he has been damaged by the ad. People might say this Baptist minister gets bombed, and since bombing is contrary to Baptist tenets, or the tenets of some Baptists including their clergy, this ad tries to say Falwell is a hypocrite. This is damaging, it is argued, to a preacher.

The newspaper library does not have a file of Hustlers and it has been several years since I saw the magazine, so I have no first-hand knowledge of the ad in question.

But it seems on the surface similar to a comedy ad in which Bess Truman is shown endorsing Plato's Retreat (a New York salon in which consenting adults are said to consent) or an ad in which Nancy Reagan is shown endorsing wire lashes for 3-year-olds who have been naughty. Such ads might be grossly offensive or they might be funny, depending on the illustrations and the texts, but they could not be taken seriously by anybody.

Mind you, there is the question of legal malice, a highly technical matter, which many a lawyer has made a good living from. But it is conceivable that if Flynt can be shown to have a personal venom towards Falwell, aiming only to make the world snicker and sneer at Falwell, then Falwell might recover damages even if his reputation was not hurt at all.

This principle is clearer to see if you forget Falwell and substitute yourself, turned into a figure of exaggerated folly in a magazine, just out of the blue, so that everybody pointed to you and laughed. You could, with any kind of competent lawyer, probably recover a nice pot of cash.

The trouble here is that Falwell is a public figure and has gone far out of his way to become one. He sets up as a moral guide; he attacks evil wherever he thinks he sees it. He identifies himself with the White House and he pronounces on a wide variety of controversial matters.

Such figures invite humorous broadsides. Is there anything in American law to protect you from rude sass when you prescribe to others how they should behave? I think not.

The truth is that Falwell is protected by law to trot about exhorting one and all to virtue as he sees it, although a few generations back he might well have been burned at the stake for various heresies. It commonly happens that minorities, once granted freedom of expression, start thinking all contrary expression is reprehensible, and start doing their damnedest to make others toe their line.

The mere fact that a man is a clergyman hardly guarantees him the license to sound off on all occasions, free from all wisecrack responses.

This case should hinge on whether the ad is a sassy wise-guy snidery (in which case no harm at all is done, and maybe a lot of good) or whether it so distorts facts in a believable way that it deeply injures the victim.

I imagine Flynt will win. It is conceivable, though, that Falwell will win and be awarded five bucks or something.

If so, it is a dangerous precedent. If you sound off all day every day on matters of morals and politics, you should not have too thin a skin. If you are a preacher, you should expect an occasional heathen to utter a raspberry.

There is substantial authority, at least in Falwell's church, that important figures of religion should have whips taken to them on occasion; and while I cannot quote similar authority that publishers of porn magazines are the elect of heaven, still the texts used in Falwell's church do suggest that whores and thieves and tavern-keepers (who are not all that much fancier than publishers of Hustler, you might think) can come out okay, at least in divine opinion.

Of course, Falwell might not only win, he might win the full $45 million. Wow. He'd give it all to the poor, I expect, since he already has a little hut to shelter him from the elements. Such a gift would be a wonderful thing, at least from a worldly and Machiavellian point of view (such gifts may or may not be virtuous) and you're almost tempted to hope he wins so the poor will get millions and millions.

But bad law is made when you start thinking how much good could flow from a bad verdict. The real question is not whether Falwell has been grievously damaged, since nobody in the world thinks he has been, but whether you can make fun of a conquering lion of Lynchburg, or whether you are supposed to fall to your knees and look around for a ring to kiss.