There are some things you just can’t do in the public parks–urinate, litter, let your dog take a dump–and among them, it seems, is conduct a political campaign.

City parks employees have been barring some volunteers for political campaigns from passing out flyers and leaflets in the city’s public parks, telling them they need a permit, one candidate charged this week.

The candidate in question? The last one you’d think the city would provoke: Norman Siegel, the constitutional lawyer who challenged the city in court 27 times over free speech as head of the New York Civil Liberties Union, and who is now running for public advocate.

On June 21st and 26th, Siegel volunteers were passing out campaign leaflets and collecting petition signatures in Tompkins Square Park when Parks employees told them they needed a permit. (The Parks Department failed to respond to repeated requests for comment.)

Siegel promptly fired off two letters to Parks Commissioner Henry Stern, pointing out that a public park is a “quintessential public forum for the dissemination of political speech” and demanding Stern write a memo to all Parks employees, reminding them that both the United States Constitution and the Park Department’s own rules protect written material–including flyers urging people to vote for Norm.

Stern eventually sent a letter July 6 that said he was “currently investigating” the incidents, but said nothing about sending a memo to employees.

That wasn’t enough for the Brooklyn-bred civil rights lawyer. “He can do the investigation, but he also needs to set forth a directive where he clearly tells people they can let people pass out literature in the parks,” fumed Siegel.

So Siegel wrote another letter: to all 350-plus registered candidates for public office, asking them if they’d had similar run-ins and offering to advocate for them if they had.

The response so far? Only one–from Public Advocate and mayoral candidate Mark Green. So far, no word from the Bloomberg camp, whose pollsters have reportedly been holding paid focus groups in the parks, showing Bloomberg ads to parkgoers and paying for their responses.

“I’m sure the Parks people just haven’t caught up to him yet,” cracked Green press deputy Jo Flattery.