Excerpt from Justice Breyer’s dissent (partially granting stay and partially denying):

If we grant the stay, the Government may begin construction of a border barrier that would cause irreparable harm to the environment and to respondents, according to both respondents and the District Court. The Government’s only response to this claim of irreparable harm is that, if respondents ultimately prevail, the border barrier may be taken down (with what funding, the Government does not say). But this is little comfort because it is not just the barrier, but the construction itself (and presumably its later destruction) that contributes to respondents’ injury.