Marvin Sontz, who runs a Phantom Fireworks sales tent in the Colonie Center parking lot, said Friday a downward trend in sales over last year is likely due to the novelty of being able to buy handheld and ground-based pyrotechnics wearing off. [...] competition has increased for vendors as more than half of New York's counties — including Albany, Saratoga, Washington, Fulton, Warren, Montgomery, Rensselaer, Schenectady and Greene counties — have opted in to the state law that allows sales within their borders. Prohibited under state law are bottle rockets and roman candles to name only a pair of the more popular holiday delights. Even if New York's relaxed rules allow only a more restricted crop of fireworks, some wonder if it just isn't clear what is and isn't permissible to light the fuse on. "A lot of people now believe that all fireworks are legal in New York," said John D'Alessandro, a Halfmoon firefighter and secretary for the Firemen's Association of the State of New York, which opposed the legalization of sparklers. Since they're doing something illegal, they don't take the time to plan that activity and think about the best place to use their fireworks.