The Enforcement Department is responsible for ensuring compliance with the Landmarks Law, which requires two things of owners of designated New York City landmarks. First, owners must keep designated properties in good repair. Second, owners must obtain a Commission permit before starting work if the work will affect a landmark’s exterior or if the work requires a Department of Building permit. Violations of the Landmarks Law occur either when work is done on a Landmark without a permit or when work does not comply with a permit.
 
A warning letter is sent to a property owner if a violation exists on a landmark under his or her control. The violation may predate his or her ownership or control of the property.  In most cases a building owner corrects a violation by obtaining a permit from the Commission and performing the work authorized by the permit.  In other cases, the Commission will require that the illegal work be modified, removed or replaced. 
 If the violation is not corrected in response to the warning letter, a Notice of Violation (NOV) will be issued. The NOV will specify a hearing date before a judge at the Environmental Control Board. Property owners still have an opportunity to avoid the hearing and avoid a fine if they respond as instructed before the hearing date.  If they do not submit the necessary paper work and are found guilty at the hearing or do not appear at the hearing, the judge can impose fines.

While there is an outstanding violation on a landmark, no Department of Building (DOB) permits will be issued for the property unless the DOB permit is for correcting an unsafe condition. Warning Letters and NOVs also appear in title searches. An uncorrected violation can be an obstacle to an owner in refinancing or selling his or her property.