Question 3: What authority do these federal officers have to detain and arrest individuals?
Insofar as federal law enforcement officers are enforcing federal law and/or state law on federal property, federal law also provides detention and arrest authorities. Of course, detention and arrest must still comport with the federal Constitution—under which warrantless arrests require probable cause to believe the individual has committed a crime.
Like most states, Oregon does authorize federal officers to enforce state law. Under
Oregon Revised Statutes § 133.245, a federal officer may arrest any person "[f]or any crime committed in the federal officer's presence if the federal officer has probable cause to believe the person committed the crime." The statute also provides, however, that "[t]he federal officer shall inform the person to be arrested of the federal officer's authority and reason for the arrest," and that "[a] federal officer making an arrest under this section without unnecessary delay shall take the arrested person before a magistrate or deliver the arrested person to a peace officer." (The statute also allows the federal officer to use the same physical force that a local or state officer would be allowed to use in effectuating the arrest.) In other words, federal law enforcement officers in Portland could have the legal authority to arrest individuals when they have probable cause for violations of federal or state law—but in the latter case, there are statutory notice and transfer requirements that, if media reports are accurate, are not being honored. But the Oregon statute also
requires state certification that federal officers have received proper training before effectuating arrests under state law before such arrests can happen. Suffice it to say, it is hardly clear that any of the federal officers have received such certification here.