Prince William County resident David C. Cline, a self-described "redneck trouble-shooter," thought it was unfair of the county to deny him a registration sticker for his El Camino pickup truck simply because he had not paid his county personal property taxes on it. So he went to court this week and won.

"They use that sticker like blackmail," said a jubilant Cline yesterday. "It is not fair for the county to blackmail you into paying . . .taxes. There is nothing criminal about not being able to pay taxes."

Prince William Circuit Court Judge H. Selwyn Smith ruled on Monday that since the county had refused to sell Cline the $15 local registration sticker he was not guilty of operating his vehicle without it. So Cline did not have to pay the five $15 tickets he had received since May.

Yesterday, assistant county prosecutor William Hamblen said, "Many people are surprised by this decision and many don't agree with it. It is too early to begin to say what the ramifications will be. This is the first court case of its kind that I know of."

Hamblen said the county has required vehicle registration stickers since 1950, and that a state law gives local governments the power to require proof that personal property taxes--levied principally on cars--have been paid before issuing the stickers.

"Requiring proof that taxes have been paid is a common practice throughout the state," said Hamblen. Judge Smith's oral ruling, which said that a county revenue law should not be used for police purposes, did not address the state law.

Cline, 63, a retired D.C. government worker, said he tried twice to purchase his annual registration sticker and was turned down because he had not paid the tax on his pickup. "I have nothing against paying taxes on my car," said Cline, who would not say how much he owes. "I'm just a year late is all."

Judge Smith's decision means Cline will not have to pay the fine but county officials said they are unsure if the ruling requires them to issue him a registration sticker.

County Attorney John Foote said he does not believe the judge's decision will mean the county must issue registration stickers to all who apply for them, whether they have paid their taxes or not. "This has to be decided on a case-by-case basis," he said.

Hamblen said the county cannot pursue the case to a higher court because under state law it cannot appeal a case it loses in criminal court. "For better or worse this judgment stands," he said.