Some of the protests are permitted while others are not. Aside from sporadic reports of projectiles being thrown at police, the protests have been largely nonviolent across the country, which is commendable and typical of the Black Lives Matter movement.*
In spite of this, many protesters are being arrested (and not just the few that were violent). On the surface, this seems not to make sense. After all, the First Amendment guarantees a right to "peaceably" assemble. It would not be unprecedented for the government to violate the constitution, of course, but is that what is really going on?
In individual cases, probably so. But in general, we must understand peaceably means more than simply nonviolent. A moment's reflection on the matter reveals why this must be so. You could nonviolently stand on someone's private yard and refuse to leave when asked. You could nonviolently stand in someone's shop and refuse to leave. Or you could nonviolently sit in the road, and assuming you have enough friends to do it with you, you might be able to prevent all traffic from passing. All of these behaviors are nonviolent. However, they are not truly peaceful because they violate others' rights. The right to use their private property as they wish in the first two cases; the right to travel on the public road in the second. Peaceful actions don't infringe on the rights of others. Thus, marching on the sidewalk is probably totally fine; marching in the road and impeding traffic probably wouldn't be.
There are exceptions to this general rule. To facilitate free speech (in theory), local governments can create rules and offer permits to say march in the road to protest, for a reasonable amount of time. While this act would still be violating others' rights to use the road in some sense, it would no longer be illegal.
As it happens, blocking traffic appears to be a preferred tactic of the Black Lives Matter group, and they are quite adept at it. Given this, it should not be surprising that many are being arrested.
The reason we call it civil disobedience is precisely because laws are being broken. They might be bad laws, but laws nevertheless. If laws weren't being broken, it would just be called civil obedience, which I can think we can all agree is decidedly less appealing.
We should hope that disproportionate force and punishment is not meted out against protesters who break the laws in the name of protest--and we should probably assume that hope will not be fulfilled in reality. But we should not be appalled, in general, that arrests are occurring. At least in the activist circles I used to frequent (all of which were on the political left), arrests were an explicit part of the strategy of civil disobedience. Arrests bring publicity and media attention to a cause that might not otherwise get it. One can debate the effectiveness of such a strategy in producing real political change, but it does not make sense to object to protesters being arrested when and if they break the law. There are ways to protest without breaking the law; the rest is civil disobedience.
With all that said, however, we would be remiss to imply the cops have been following the letter of the law in response to the protests. A particularly interesting example of this recently occurred in Louisiana, when a group of protesters ended up leaving the street for private property. The protesters reportedly had the property owner's permission, and thus were fully within their rights to remain there. In spite of this, the cops eventually evicted them with a highly militarized response, even as the property owner tried to object.
The thin rationale used to justify this action by the police was that the protesters had already broken the law previously by walking on the road. Based on the sequence of events summarized by Reason, however, this does not make sense. Here's the relevant excerpt:
She says the protesters held a peaceful rally outside the state Capitol, then a portion of them attempted to march along the Interstate highway (a common Black Lives Matter tactic) but were blocked by the police and diverted to a city road.
Reason is citing one of the protesters here, so there's no reason to assume she's an objective observer. Still, the group clearly managed to get from the interstate (where they allegedly broke the law) to private property in what appears to be a subdivision. If the walking on the interstate was illegal, the police could have arrested them at that time.
Instead, they chose follow them to private property and arrest them there. For this to be legitimate, we would have to assume the police actually tracked exactly who in the protest group did and did not violate the law. Then in the chaotic mess that followed in the front yard, they judiciously identified those same people for arrest. Watch the video below, and then see how likely you think that explanation is.
What seems more likely is that, in the most generous scenario, the police may have observed some people breaking the law in the group and opted to use this as a pretext to invade private property. This response probably had nothing to do with identifying the actual individuals who violated a law, and everything to do with sending a message. In other words, it would appear to be thinly veiled collective punishment, with an innocent property owner's rights violated in the process.
It may be worth debating the usefulness of civil disobedience as a tactic, but it should be relatively easy to know when it occurs. And arresting protesters based on their violation of laws is not suppressing their First Amendment rights. It's just the logical outcome of protest actions that involve civil disobedience, for better or for worse.
But we'll end on a slightly more optimistic note. In the example cited above, a group of generally left-leaning individuals appropriately invoked private property rights only to see the government officers gleefully violate them with impunity. For libertarians, that's a perfect metaphor for government action writ large. Maybe some good will accidentally come from more people seeing that.
*It probably goes without saying, but the tragic police shooting in Dallas last week which claimed the lives of 5 officers was not affiliated with the protest that preceded it. The attacker used the event as an opportunity, but there's no evidence of coordination. People have used the event to assign blame to Black Lives Matter based on unassailable collectivist logic--the attack occurred in the vicinity of a peaceful Black Lives Matter protest, the attacker was black, ergo, Black Lives Matter is at fault. It's not clear whether the assailant was even sympathetic to the Black Lives Matter movement before he decided to commit the crime. Even if he was, it still would not warrant smearing the entire organization. A group cannot be justly judged based on the actions (or opinions) of its craziest members; otherwise none of us could ever bear to identify as anything. For example, I couldn't call myself libertarian now that the Iraq War-supporting Bill Weld has adopted the moniker. I also probably couldn't call myself vegan, given that some Canadian vegans went off the deep end and got a ruling passed that prevents discrimination against vegans. I deeply wish I made that up, but sadly, I did not.
I'm digressing in a footnote now, which may be a new low, but the point here should be clear. It is not correct to judge an entire group based on the actions of a single member. And this is particularly true of groups and identities that one does not voluntarily adopt (their race, national origin, religion (arguably), etc.).