Our neighbor pushed back the slope on their west side of front yard and installed a 9 foot retaining wall leaving about a foot of their property line next to ours. Leaving us to maintain it since 1998 when we all first moved into the development. This 2nd owner neighbor moved into the house 6 - 7 years ago, re-landscaped the front yard & left the foot of the same property line for us to maintain. Until a week ago, they decided to send us a certified letter to "cease & desist" & remove the ground cover we have put in on this one foot of their property line. They gave us 30 days to remove it, otherwise they will seek damages thru court order against us. Are we liable to comply & do anything? Does this fall into the 5 year real estate abandonment ?