The police do have a broad degree of authority as far as searching your brother and his surroundings and belongings if he is still on probation. The details vary by state. We aren’t qualified to give specific legal advise as it relates to your case. You need to have your brother contact an attorney to see what is and isn’t legal in your state/jurisdiction. We always encourage filming the police.
About a year ago my younger brother was caught with a hand gun and taken into custody and charged with a misdemeanor. He has was placed on house arrest where his probation officer made a mistake and left him on house arrest for 20 additional days. Since then he is going to college and staying out of trouble, but the police officer who arrested him keeps harassing him constantly pulling him over and the other day showed up at my mothers house with eight additional officers claiming that he was there for a probation search. He claimed to be his probation officer, but he has not had one assigned. The officers went through all off my brother belongings and took a camera sim card claiming that it was evidence. Do they have the right to do this?