Several recent studies have found a positive, statistically significant correlation between ratification of human rights treaties and respect for human rights. Some commentators have interpreted these results as evidence of the causal effect of international human rights law on human rights outcomes. We revisit this debate and present evidence that for two treaties — the Convention on Elimination of Discrimination Against Women and the Convention Against Torture — these results disappear once time trends are taken into account. Our evidence suggests that recent improvements in human rights are attributable to long running trends that pre-date the emergence of the relevant treaty regimes.