Not only is it not true it's not even legally required.The police do not want the general public to comprehend this fact. That is, until in a courtroom when the police are being sued. The general public are very ignorant about both police protection and national security.
I'm not shirking the responsibility of the general public but there is a lot to be said for gubment efforts to effect that end...
We have been too long living the good life here. A little strife is in order to get us in the right midset again.
EBUCK