If mines were planted south of the MDL, isn't that a territorial violation?

If it is south of the MDL, isn't that our territory?
The reason this landmine incident is controversial is because
North Korea planted the mines south of the MDL,
which constitutes a localized provocation and territorial violation,
so I believe the UNC also views it as a violation of the Armistice Agreement.
What I am curious about is whether the MDL line itself is unclear?
Looking at the Ministry of National Defense press conference,
it seems like there isn't a clearly drawn line regarding the MDL between them and us.