Final answer:
Officers can make a warrantless arrest under the Illinois Domestic Violence Act of 1986 if they have probable cause to believe a protection order has been violated.
Step-by-step explanation:
According to the Illinois Domestic Violence Act of 1986, an officer may make a warrantless arrest for a violation of an order of protection if they have probable cause to believe that the order has been violated. This aligns with general legal standards that permit warrantless arrests when probable cause exists, especially in cases involving felonies observed by the officer or in instances where there is evidence of a crime committed in their presence. While the act specifically addresses protection orders, it's in harmony with broader principles regarding police authority and the Fourth Amendment, which require reasonable suspicion or probable cause for most search and arrest scenarios without a warrant.