LONDON (AP) — Dozens of giggling demonstrators have inhaled laughing gas outside Britain's Parliament to protest government plans to ban it and other "legal highs."

The Conservative government has announced a crackdown on psychoactive substances, drafting a bill to outlaw the sale for non-medical purposes of mood-altering drugs, excluding alcohol, nicotine and caffeine.

The ban would include nitrous oxide, also known as laughing gas, which is used as a dental anesthetic and also taken recreationally by weekend clubbers.

Protesters on Saturday filled balloons with the gas and breathed in, many erupting into giggles on the Parliament Square lawn.

Protest organizer Stephen Reid of the Psychedelic Society said psychoactive substances "can be risky, but it should be for individuals to decide whether or not to take the risk."