The interest of Conflit-Driven Clause Learning (CDCL) [7] in SAT solving is well established. An adaptation of CDCL to Constraint Programming have been introduced in [14,15]. However, for the algorithm to run on global constraints, there is still a need to specify for each of them the explanation rules. This is a huge obstacle on its standardisation in off-the-shelf solvers. In this paper, we propose a method to automatically generate explanation rules from any constraint decomposition.