legalise

To legalise is to make something lawful. Legalise the practice, legalised in 1967, campaign to legalise it.

It is not the same as decriminalise: legalising means the state regulates and permits the thing, where decriminalising only removes the penalty and leaves it unregulated, and that difference decides most drug policy arguments. This is the British spelling; American writing has legalize.