The NGO. led by the ruler, Tuanku Abdul Halim Mu'adzam Shah's cousin, Syed Idrus Syed Baharom, said the institution should not be toyed with.
"Tuanku is the ruler of the country, he is not an administrator. Why was he even dragged into this?" Syed Idrus asked at a press conference in Alor Setar.
"This is a warning to all and we don't want to hear anything else like this," he is reported by Berita Harian as saying.
Nawawi had initially said that 'Malaysian Official 1' in the United States Department of Justice lawsuits cannot be the prime minister, arguing that that constitutionally, the PM answers to the Agong.
He said this in a Facebook comment, but later amended the post.
He then denied referring to the Agong and lodged a police report on this.
He also denied referring to 'Malaysian Official 1', instead arguing that he said 'Malaysian Official Number 1'.
Malaysian Official 1 in the US lawsuits is described as a high-ranking Malaysian government official, who received US$731 million, which originated from 1MDB, and is related to PM Najib Abdul Razak's stepson Riza Aziz.
US attorney-general Loretta Lynch said 'Malaysian Official 1' is not identified by name as the lawsuit as it is not required to meet the objective of seizing assets worth more than US$1 billion, believed bought using money stolen from 1MDB.
Nawawi is being probed by police over this Facebook comment.
Najib has denied using public funds for personal use, while attorney-general Mohamed Apandi Ali has cleared Najib of wrongdoing.