Martin S. Bradley thought he was only expressing his political opinion when he scrawled his objections to Reagan administration policies in Central America across his tax return and mailed it to the IRS on April 15, 1984.

After all, Bradley reasoned, his income was so low in the previous year that he owed no taxes and was not even required to file.

The tax people were not amused. The IRS slapped Bradley with a $500 "frivolous"-return fine, a penalty that a federal appeals court upheld. Bradley's handwritten protest generated what is believed to be the first case of penalizing a taxpayer who owes no tax.

"If I pay, I'll pay under protest," said Bradley, an antiwar activist who directs a soup kitchen in Ukiah, Calif.

For years, Bradley had dutifully filed tax returns and paid taxes. But because his teaching post in 1983 provided free room and board, his income fell below the $3,300 level at which he would have owed taxes.

So Bradley filled in his name, address and Social Security number on Form 1040 and wrote: "In watching the U.S. Governments intervention in Central America and the deployment of omnicidal nuclear weapons, I can no longer be complicit by paying taxes. My allegiance is to the law of a higher spirit, the law of God."

The IRS promptly sent back two blank returns and asked Bradley to file a "proper tax return." A month later, the agency assessed the $500 penalty.

The 9th Circuit Court of Appeals in San Francisco, agreeing with a federal district court, upheld the IRS in May.

The court contended in 29 sober paragraphs that the Form 1040 Bradley filed "purports to be a tax return" and "takes a frivolous position," among other sins.

Bradley's attorney, Susan Sher, points out that the same words would have engendered no penalty had they been written on a blank sheet of paper.

"My fear is that this sets a very dangerous precedent for someone who wants to contact their government and does not use the proper form," she said.