I agree in part. Hypothetically, the fight (even based on assumption of the risk/contributory negligence by both mutual combatants), trips, falls or otherwise injuries themselves because of a known dangerous condition o the property (e.g. Open Hole, inadequate lighting, broken stair rails/stair case, etc), then Yes, they could sue and even overcome a Motion to Dismiss based on Summary Judgment on a Notice issues on the subject property. I agree with the others. We get lawsuits all the time based on premises liability. Make sure to carry good general liability insurance and have an excellent commercial leasewith a strong contractual indemnification clause. Also, this fight should give you notice that this Tenant has control issues. Thus creating a known dangerous condition on the property if another fight incurs and a third party is injured. If they cannot control their employees, then what else? I would be concerned if we represented the Owner's and try to prevent exposure is a good idea. A careful review of the lease is a good idea.