Lease conflict over renters parking in yard?

Alright, I recently entered into a lease agreement at the beginning of January into a duplex. It's located in a very nice residential neighborhood in a historic district, so many of the houses are old fashioned and very nice. The duplex does seem out of place there next to these beautiful homes. Anyway, my room mate likes to have people come over quite frequently, and since the drive way (which is not paved and nothing more than a set of dirt marks) sometimes people park on the front yard. Keep in mind, this is no pristine lawn by any means. Partial dirt, weeds, spits of actual gr. Anyway, I received a notice on my door this morning stating that "The owners have witnessed vehicles parked on the front yard, and if the issue is not resolved in seven days, the renters will be evicted". There is nothing explicit about parking on the yard in the lease, by the way, and now I have an obligatory meeting with the owners to discuss and resolve the issue. And I will admit that it gets a little ridicules when my room mate decides to have an impromptu party. But again, it's not like this is a "home & gardens" type of house and front lawn. But am I in the wrong? What should I do?