On Sunday morning, a group of animal-lovers will march a mile down one of Havana's main thoroughfares waving placards calling for an end to animal cruelty in Cuba.

Short, seemingly simple, the march will write a small but significant line in the history of modern Cuba. The socialist government is explicitly permitting a public march unassociated with any part of the all-encompassing Communist state, a move that participants and historians call highly unusual and perhaps unprecedented since the first years of the revolution.

Still, there is no indication Cuba is moving toward unfettered freedom of assembly: The state still clamps down on unapproved political speech with swift and heavy police mobilizations, waves of arrests and temporary detentions.