WASHINGTON (States News Service) -- Model rocket hobbyists, arguing the future of the sport is in jeopardy, are turning to the courts to seek relief from increasing government regulation.

Fired up by recent actions to crack down on the sport practiced by thousands, rocket hobby associations are engaged in a legal battle with the Bureau of Alcohol, Tobacco and Firearms over its classification of the key ingredient used in rocket motors as an explosive.

A model rocket hobbyist and her rocket

The mounting paperwork and costs required to launch model rockets is having a chilling effect on the hobby, said Tripoli President Bruce Kelly. The sport already faces regulation from the Transportation Department, the Federal Aviation Administration, and other agencies.

The classification of rocket motors as an explosive means that new users, who already must obtain $100 licenses and pass a written test, must buy new safes to store rocket motors, and apply for additional permits.

"It's already hurt the sport to some degree," Kelly said, adding that the magazines to store motors run between $200 and $600. "A lot of people are just not going to join if that's going to be a requirement across the board."

Model rocketry has grown more sophisticated since the metallic rockets of the 1950s and 1960s. Unlike the plastic toy rockets one can buy in a toy store, high-powered rockets, made of cardboard, plastic and wood, and measuring as wide as 2 inches (5 centimeters) and as tall as 8 feet (2.5 meters), are only available by mail order. With more powerful thrust and a taller launch range than standard model rockets, the larger rockets require permits.

The legal debate focuses on the fuel, a fast-burning substance called ammonium perchlorate composite propellant. Bureau of Alcohol, Tobacco and Firearms (BATF) attorney David Wolf said the pale green substance has been on the agency's explosives list alongside other dangerous materials since 1971.

The Tripoli association, a nonprofit organization based in Otem, Utah that regulates all high-powered rocket launches among its 3,800 members, argues in its legal document that the BATF's actions were "arbitrary, capricious, an abuse of discretion and/or not in accordance with law."

No one has been killed or injured by a model rocket, group members say.

"This stuff is no more dangerous than a can of propane under your grill or a can of spray paint," said Bill Spadafora, a plumbing contractor and high-power rocket hobbyist in Saugus, Massachusetts.

Spadafora said a federal agent paid a visit to his home last year and asked to inspect his magazine, a metal box storing his rocket motor in a shed behind his house.

Wolf denied the agency was strengthening its laws on rocketry, and said there were incidences of criminal use of the substance. He refused to discuss further details of the case.

The sport already faces numerous federal rules and self-imposed regulations. The Transportation Department, the Federal Aviation Administration and the Consumer Product Safety Commission set rules about when and where a rocket can be launched, and where it can be stored.

While the sport attracts everyone from former astronauts to aviation nuts, as well as lawyers and carpenters, its costs may become too high, said John Kyte, the lawyer who is defending the associations.

"The bottom line concern is that their regulation would drive the cost up so high that it would make it impractical for the average person to participate," Kyte said. "They haven't got anything on which to base this concern they claim to have."

The groups have posted developments in the legal squabble on their website, and have even opened a legal defense fund to build their case. "We have a strong legal case," the National Rocketry Association's site says. "But money will be required to finish what we're starting."