The issue of biological contamination in space exploration has highlighted the relevance of addressing the ethical and legal responsibilities entailed in exploring previously undisturbed regions of space, especially those which have the potential to harbor life. While the scientific importance of space exploration means that the introduction of spacecraft into otherwise undisturbed environments is a necessity, the extent to which environmental disruption can be considered a responsible use of a shared space, has not been consistently identified in the scientific or legal literature. This paper discusses some of the key legal and ethical issues concerning the responsible use of space from an astrobiological and planetary protection perspective, as well as proffering recommendations as to how international space law can create more effective ethical responsibility and liability standards regarding the biological integrity of space-based environments.