The decision is here; some key paragraphs:
The gravity of Mr. Sirhan’s crimes alone counsels against his release. But I have concluded that he is unsuitable for parole because he poses a current threat to public safety. After decades in prison, Mr. Sirhan has failed to address the deficiencies that led him to assassinate Senator Kennedy. Mr. Sirhan lacks the insight that would prevent him from making the same types of dangerous decisions he made in the past.
The most glaring evidence of Mr. Sirhan’s deficient insight is his shifting narrative about his assassination of Senator Kennedy, and his current refusal to accept responsibility for his crimes. As the following examples show, Mr. Sirhan has inconsistently described his role in the assassination of Senator Kennedy, claimed shifting memory lapses, minimized his participation in the crimes, and outright denied his guilt….
But Mr. Sirhan’s risk of committing acts of interpersonal violence is not the most relevant indication of his current risk level. As explained above, Mr. Sirhan poses a risk to public safety because he lacks insight, as demonstrated by his refusal to
accept responsibility for the assassination of Senator Kennedy, his failure to renounce political violence, and his lack of the requisite skills to manage complex external triggers. Thus, evidence of Mr. Sirhan’s diminished physical strength does not mitigate the serious threat to public safety that he currently poses, including the risk that he may incite political violence should he be released on parole. Accordingly, his release is not consistent with public safety.
I can’t speak to the merits of the Governor’s decision, since I know little about parole practices generally. But I should note that, while someone can’t just be put in prison based on a “risk that he may incite political violence,” decisions about parole for people who have already committed political violence may indeed generally turn on such matters.