My brother was caught drinking with a friend outside two days ago. The police charged him under sections 107/151 and he was released on bail the next day. Is this a valid action by the police? Can I challenge this? Can we get the bail revoked? What would be the costs and time involved in pursuing a higher court appeal?

The police action of charging your brother under sections 107/151 for drinking with a friend outside is likely valid as these sections pertain to preventing breach of peace. You can challenge this in a higher court if you believe the charges are unjustified. Revoking bail after release is difficult and the costs and time involved in pursuing an appeal would depend on the specific legal arguments and court procedures.