I only did that once, take action. I was in the US in an apartment with gated parking spot assigned to me.
I called the tow service becuse somebody parked in my spot. All I had to do was show my lease and the document clearly assigned the spot to me to me.
I felt bad but, my only extra option was to park nearby on the street and I did that before because of these prats and I was fined. 60 or 80 dollars don't remember. Irvine California, No parking on streets allowed