The article discusses mainly negative legal aspects considering both, the applicable law and the theory of law, of the Multilateral Convention to Implement Tax Treaty Related Measures to Prevent Base Erosion and Profit Shifting ("MLI") with the focus on whether the MLI was implemented in the Slovak legislation in compliance with the mandatory legislation process, whether the MLI will apply also on double tax treaties currently being negotiated or also an impact on a legal certainty of users of the Slovak law. It contains an anticipation how these negative aspects can be overridden by the interpretation of the applicable law as well.