This work considers implementation of requirements expressed as High-level Message Sequence Charts (HMSCs). All HMSCs are not implementable, and the question of whether an HMSC speci cation can be implemented by communicating machines is undecidable in general. However, several subclasses such as local HMSCs can be implemented using a simple projection operation. This paper proposes a new technique to transform an arbitrary HMSC speci cation into a local HMSC, hence allowing implementation.We show that this transformation can be automated as a constraint optimization problem. The impact of modi cations brought to the original speci cation can be minimized w.r.t. a cost function. The approach was evaluated on a large number of randomly generated HMSCs. The results of this experimentation are presented and analyzed. In particular, the evaluation shows an average runtime of a few seconds, which demonstrates applicability of the technique.