Ukraine Military Code for its security/intelligence agency?

According to this Wall Street Journal article, Ukraine's President has removed both its top prosecutor as well as the head of the Security Service of Ukraine, or SBU, based on allegations of widespread collaboration with Russia -- treason -- within their respective agencies. The SBU is described by the Journal as "Ukraine's main security and intelligence agency ...  separate from the GUR military-intelligence agency that plays the primary role in the war with Russia." Interestingly for this blog, the article reports that Pres. Zelensky "removed Mr. Bakanov under a military disciplinary code that cites 'negligence in performing duties that caused loss of life or other grave consequences.'” Inquiring minds want to know why the SBU Chief falls under military justice in Ukraine, and if the civilian criminal justice system is better suited for those not in the military.