tell that to the people of Rwanda and Srebrenica, and that's just to start. they can protect civilians if it doesn't jeopardize the mandate they have. the problem with that is the UN security council has five members with veto power and a global interest in maintaining many conflicts for the purposes of imperialism. historically, there have been a lot of times when protecting civilians from being brutally murdered wasn't politically convenient.

having the legal authority to intervene or even protect yourself doesn't mean shit if you don't have the ability or political power to do so. russia is a member of the security council with veto power. the security council oversees UN peacekeepers. the very people the peacekeepers would be protecting civilians from are the people who can veto their ability to protect civilians. which is why, if you carefully read that article, the official never once says they would be allowed to protect civilians, and specifically mentions that any engagements would be “defensive in nature”.

the UN is a absolutely worthless organization when it comes to stopping powerful countries from doing terrible things. it has absolutely zero ability to protect the civilians in Ukraine from further russian imperialism or ethnic cleansing.