Ari Setiawan Niti Sumita as a member of the Indonesian Advocates Association (PERADI), he is licensed to practice in all Indonesian jurisdictions. Ari Setiawan Niti Sumita is primarily involved in litigation practice. He has been extensively involved in litigation cases, including criminal cases where he represented high-profile individuals in corruption cases, particularly in government institutions. Currently, Ari Setiawan Niti Sumita is handling a high-ranking official involved in alleged gratification and corruption.

Ari Setiawan Niti Sumita has also been involved in multi-trillion rupiah contract disputes involving major gold mining companies and commercial disputes over intellectual property rights between major electronic appliance brands. He is also experienced in handling bankruptcy cases and cases proceeding in the Administrative Court and the Constitutional Court of the Republic of Indonesia.