Some people also steal & murder. So do some cops. Lying or killing are, before the law, criminal. No matter who does it. However, this ruling has expressly allowed perjurous cases to go unpunished, as long as they are aimed at police officers.
I'm reasonably sure they are already illegal. The moment an officer signs the paperwork, it becomes a legal document & intentionally lying on a sworn document is, in itself, a criminal offense. I'm not 100% on that but it seems reasonable.false statements in support of officers were not also criminalized.