When there is a line at a restaurant do you cut the line?

Is there laws in place to deal with people who cut the line?

If the answer to both of those is no, then you've already participated in a system in which group decisions are adhered to, without any enforcement mechanisms. And arguably, the group decision to wait in line instead of cutting is a democratically decided one. Nobody likes having somebody cut in front of them, so most people prefer that waiting in line is adhered to.

That's just a small thought experiment, applying the same rational to larger society is straightforward. And these kinds of things already exist in the form of community gardens, mutual aid orgs, really really free markets, community cleanups, community workshops, and other similar things. Some of these are set up as nonprofits out of a necessity of working under capitalism, but not all of them. And they work together despite nobody enforcing usage or contributions.

They are also democratic, if the group working the local community garden decides as a collective that the existing garden is too small, they may find that they agree to expand it by adding an extra row of beds along some section of the plot. This is also, all without enforcement.