In the April incident, Ivan Amelchanka was photographed standing next to a man who was using a hand-held camera to film an opposition-organized march in Minsk.
The activist's placard contained the word “Musorok” -- a Russian slang word that can be translated as "fuzz" or “pig."
It also had an arrow pointing in the direction of the officer.
Amelchanka was arrested on May 17.
In issuing the 15-day sentence, the judge ruled that Amelchanka’s behavior fit the Belarus authorities' definition of hooliganism.