The incorporation of environmental variables into policies, programs, plans and projects has been achieved through the use of an Environmental Impact Assessment (EIA). However, the recognition by scholars of several limitations of the EIA has prompted the consideration of Strategic Environmental Assessment (SEA) as the appropriate instrument for achieving this objective. Studies on SEA have concentrated in phases prior to the decision-making, despite the fact that, after the strategic decision has been made, it is also necessary to follow up on the environmental impacts or effects produced by the plan, as well as the possibility of adopting measures to correct them when they cause adverse or unforeseen effects. The way in which this following-up takes place will vary from country to country, based on the respective legal system. Therefore, this study aims to understand these forms of follow-up in urban land planning instruments, at the local level which are legally binding, comparing regulations in France, Portugal and Chile, through three research questions focused on determining whether this phase exists, whether it is possible to modify the local planning instrument in the event of adverse effects and whether there are offset measures for those effects. This study employs a mixed methodology based on the law and content analysis, enabling the identification of pertinent aspects for investigation, the compilation of material for this study, and the answering of research questions through the comparative analysis of the laws of the selected countries. Results show differences and similarities between the regulations of the countries analyzed, regarding the ability to reverse undesired, negative or different effects from those originally considered in urban plans. It will shed light on the possibility for other countries to take follow-up action in the face of undesirable scenarios in the application of planning instruments. The gaps found in our research may also exist in the legislation of other countries.