In the new generation of message-based systems such as network-based smart systems, distributed components collaborate via asynchronous message passing. In some cases, particular ordering among the messages may lead to violation of the desired properties such as data confidentiality. Due to the absence of a global clock and usage of off-the-self components, there is no control over the order of messages at design time. To make such systems safe, we propose a choreography-based runtime enforcement algorithm that given an automata-based specification of unwanted message sequences, prevents certain messages to be sent, and assures that the unwanted sequences are not formed. Our algorithm is fully decentralized in the sense that each component is equipped with a monitor, as opposed to having a centralized monitor. As there is no global clock in message-based systems, monitors may prevent the sequence formation conservatively if the sequence consists of concurrent messages. We aim to minimize conservative prevention in our algorithm when the message sequence has not been formed. The efficiency and scalability of our algorithm are evaluated in terms of the communication overhead and the blocking duration through simulation.