Ice has detained American citizens and has conducted warrantless searches.
That is too vague, were these searches a violation of the law? Police do not need a warrant if they have probable cause. However,
if probable cause does occur, such as a suspect runs away, a gunshot is heard from another room in a home, or even when an individual makes a sudden movement, a search becomes legal without a warrant.
No, police generally do not need a warrant to search if they respond to a 911 call, but only if there is a clear and immediate emergency situation, such as a crime in progress, a threat to life, or a risk of evidence being destroyed; this is known as "exigent circumstances" and allows them to enter a property without a warrant to address the emergency.
So what are you saying, do you have evidence that they committed warrantless searches but did not have probable cause or exigent circumstances?