The consistent look of the condo common area is gone

In our Bylaws, it is stated that we must not plant or put anything decorative in the common area in front of the condo. It is a consistent look with certain bushes and one kind of flower. 

I am in agreement with this but several owners have taken it upon themselves to plant and put in decorative objects. The consistent look has disappeared. No one wants to say or do anything but complain about the look. The association does nothing. Please, advise me on this.