We study the effects of treaty design and domestic institutional hurdles on the ratification behavior of states with respect to multilateral environmental agreements (MEAs). Specifically, we examine whether (1) strong legality mandated by a treaty such as precisely stated obligations, strong monitoring/enforcement mechanisms, and dispute resolution procedures, and (2) high domestic constitutional hurdles such as requirements for explicit legislative approval deter countries from ratifying a treaty. To test our theoretical claim, we use a new time-series-cross-sectional dataset that includes information on the ratification behavior of 162 countries with respect to 220 MEAs in 1950-2000. We find that treaties that are characterized as 'hard' indeed deter ratification. Furthermore, explicit legislative approval requiring supermajority also makes treaty ratification less likely.