Major e-commerce firm Inc. sued the government Monday over legislation enacted last month to restrict online sales of certain over-the-counter drugs, calling the new rule an "unconstitutional" impingement on freedom of business. filed the suit with the Tokyo District Court, seeking an injunction to have the restriction revoked.

With the December revision, the pharmaceutical affairs law will stipulate that certain over-the-counter drugs recently considered prescription drugs won't be eligible for sale online for three years to allow for a safety assessment to be conducted. The new rule is expected to take effect this spring.

The health ministry has said the three-year wait is necessary to examine the risk and severity of side effects.