INS (at the time, now ICE) detainers don't meet the same level for folks who aren't citizens.

Everyone there has no coverage, at all, under any circumstances. If you enter our land and end up in the custody of the federal government in reason to your status being unlawfully alien (which this was, whatever the opinion on it) any possible coverage you get is forfitted, as is any possible "worldwide travel insurance" or anything like that.