Question about for lease sign on commercial property

[Kenric Hwa]

Hello, we just leased an entire commercial building. Next to the sidewalk on the building is the FOR LEASE sign for the building that was put in place when the building was empty. This is a wooden sign set about 2 feet inside from the sidewalk.  I asked the leasing company to remove the sign since we had leased the entire building. They said that they want to keep the sign up because it provides them advertising for other empty properties.

My question is, do they have the right to put a sign there? I don't know if I have the rights to the entire property boundary or just the building and parking lot. They hire the landscapers who come once a week. My lease in NNN.

Thanks.