If the law is arranged arbitrarily and difficult to fight, the public will consume it without chewing, and then vomit it back up creatively into daily reality, according to each taste.
It is hard to digest with common sense why an understanding is considered as threatening a state; let alone if the understanding is similar to Marxism. It will be much stranger if the reason for forbidding it is that the understanding is deemed contrary to Pancasila. This strange but real thing is called the Criminal Code, or KUHP.
Marxism was present in the Dutch East Indies colony before this region was called Indonesia. Together with other isms, Marxism encouraged the struggle for Indonesian independence before the birth of Pancasila. Thanks to the establishment of Pancasila as the foundation of the state (1945), this pluralistic nation could unite, become independent, and tolerate each other despite the differences in ideologies, understandings, and isms.