France, Feb. 8 -- The European Court of Human Rights (ECHR) on Thursday found France guilty of unlawfully employing a controversial police tactic to encircle protesters during a 2010 demonstration.

The method, known as "kettling", consists of police cordoning off areas to contain groups of protesters in a small space- sometimes for hours- until in the police's view, they can no longer cause trouble.

Police used the tactic at a 2010 demonstration in Lyon, southeastern France, against pension reform under then-president Nicolas Sarkozy - which sparked violent clashes between protesters at police in several French cities.

While acknowledging that there were good reasons to cordon off the city's Place Bellecour square to stop unrest spread...