Comment by lazide
Police in general don’t need to show warrants to arrest people. In high profile situations it may be done to minimize political blowback, but clearly that is not a primary concern in this situation (except toward individual officers, which is why they are masking).
In many situations, they just need a documentable/articulable (to a judge, later) reasonable belief that a crime was occurring in their presence, or in other situations that a specific crime had occurred and there was a reasonable belief that person had committed that crime.
Resisting arrest, and impeding official business of a police officer are usually arrest-able offenses almost anywhere.
Details vary by jurisdiction and crime, but ‘you need a warrant to arrest someone’ is an edge case, not the common case. In those cases, it’s also often an indictment or bench warrant.
That all makes sense, but these don't look like police officers — these are guys wearing backwards baseball caps and surgical masks. Effectively, our trust that someone holds position of authority in law enforcement is based on their uniform and badge.
If we normalize some dude in a mask and a baseball cap as someone that has the authority to arrest you and put you in an unmarked van, that represents a real and serious breakdown of trust and order in society.
ICE agents should wear a real uniform (ICE with their real name), have uncovered faces, and be required to show badge/authorization upon request -- otherwise members of society have to reason to trust them (or people who look like them).