Yesterday was March 31. Which in Russia always means one thing: Peaceful protesters were arrested for doing nothing more than going outside to demand their right to peacefully protest.

Since late 2009, Russian human rights activists have embarked on a effort they have dubbed “Strategy 31.” On the last day of each month with 31 days, these activists take to public squares in Moscow, St. Petersburg, and elsewhere to demand their constitutional right of freedom of assembly. They have chosen to hold these protests and rallies on these days because it is Article 31 of the Russian constitution that provides this right, although the provision now exists in name only. So the activists once again came out to demand that Russian authorities abide by their own laws. And, predictably, Russian police officers detained scores of protesters. In Moscow, police arrested 54 people in a rally at Triumph Square, and in St. Petersburg, more than 100 people were arrested, including opposition leaders Boris Nemtsov and Ilya Yashin.

Why have Russian human rights advocates — some of whom disagree on most questions beyond the fact that they are living in an authoritarian regime — been so dogged in rallying to fight for this one freedom? Because, as Ludmilla Alexeeva, a former Soviet dissident and veteran human rights activist, told me, “We must have this freedom to march in the streets with our slogans, flags, and demands. Out of all the civil rights, this right, the right of freedom of assembly, is the most important.” In her view, gaining this right is essential because it is the foothold from which all other rights can be demanded.

She is right. And unfortunately, most authoritarian regimes know it, too. For example, the Chinese Communist Party has long understood this point. In the past 20 years, Beijing has relaxed many of its previous prohibitions, including those on private property, the ability to travel, and to receive some legal protections. The press is not free, but it is freer. Even the dreaded one-child policy appears ready to be lifted. But freedom of assembly? Not close.

I saw this firsthand in February in Beijing. Anonymous calls circulating on the Internet asked people to congregate at one of roughly 20 sites in cities across China. At 2 p.m. on a Sunday, people were supposed to simply show up and “go for a stroll.” I was in Beijing, so I went to the site there: a high-end shopping area called Wangfujing. I arrived more than an hour and half early. I have never seen so many police and plainclothes security officers cover what amounted to one city block. Estimates by others there were of 500 to 700 police officers and 1,500 to 2,000 plainclothes personnel. As I walked down the street, at some points, nearly every third person had an earpiece sticking out from their collar. The regime made a show of force, but its insecurity at the prospect of people simply “going for a stroll” was on full display. The message: You will not assemble.

And it is because of the essential importance of this right that many Egyptians are so alarmed by the edicts being issued by their military government. Last week, the government issued a decree that would ban any strikes or protests that could arguably harm the economy. Under Hosni Mubarak’s regime, any unregistered gathering of more than four people was officially illegal. That is in part why it took the protests in Tahrir Square — a gathering of more than a million Egyptians — to bring the regime down. Egyptians are understandably concerned to see the one weapon they wielded so effectively be outlawed in a matter of weeks.

So, in Russia, the struggle for people to come together and express a common purpose will continue to remain a battleground. With one difference: The activists behind Strategy 31 say they will now come out to fight for this right at the end of every month, with or without 31 days.