Two groups of men stood on opposite rooftops perched on a hillside overlooking Rio de Janeiro's Ipanema beach, taunting one another. It was a macho showdown between opponents wielding unlikely weapons — kites. On this July morning in the impoverished neighborhood, they were using taut, sharp-edged kite lines — known as "cerol" in Portuguese — to slash their opponents' lines, ripping their kites from the sky.

Kite fighting has caused horrific injuries and even deaths, and a bill moving through Brazil's Congress is seeking to prohibit the manufacture, sale and use of the razor-sharp lines nationwide, with violators facing one to three years in prison and a hefty fine. The lines are already outlawed in some congested areas of Brazil, including Rio, but that didn't appear to trouble the men jousting with their kites above Ipanema; indeed, some of those flouting the law were police officers. A couple of them called kites their therapy.

"That's the logic of kite flying: cutting another person's line," said Alexander Mattoso da Silva, a military police officer with bulging, tattooed biceps. He goes by "Jarro" and in 2014 he traveled to France to test his mettle at an international kite festival, where he won the kite-fighting competition. "We always try to fly the kites in suitable places to not put anyone at risk.

There's no risk here, because the kite falls into the woods," Jarro said, pointing to the tree-covered mountain above which the kites were dancing. Still, there wer.