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International Law and the Credibility of Commitments

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Principal Investigator(s):

Geoffrey P.R. Wallace
Rutgers University
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Sample size: 3528
Field period: 02/02/2013-03/27/2013


Recent research on international law suggests states use international legal agreements as a commitment device to increase the credibility of their promises. Yet empirical studies reveal conflicting or ambiguous findings that legalized commitments are indeed more capable of signaling to other parties the willingness and capability of a state to subsequently comply with its promises. Testing this credibility mechanism has been complicated by selection effects both in a state’s decisions over designing and joining an agreement in the first place, as well as its likely anticipation of the consequences of subsequent noncompliance. This project uses an experiment embedded in a national survey to estimate the effect of legalization on the credibility of a country’s commitments, which is measured by the beliefs that the country will comply with its promises.


More legalized commitments are expected to be viewed as more credible compared to a situation where the country made no prior formal promise. This study examines one element of the credibility of commitments, which is operationalized as the beliefs of a domestic actor (in this case the U.S. public) that a foreign country will subsequently comply with different types of legalized commitments. Drawing on the existing international law literature, as well as the broader study of commitments in international relations, the hypotheses are as follows.

1) An increase in the level of legalization of a commitment should be associated with an increase in the expectations that a country will comply with its promise.

2) A country with a prior history of violation/compliance should decrease/increase expectations that the country will comply with its promise.

3) Legalizing a commitment should have a greater effect on expectations of compliance for countries with a history of violations compared to those with a history of compliance.

4) Legalizing a commitment should have a greater effect on expectations of compliance in lower stakes issues compared to higher stakes issues concerning national security.

5) Legalizing a commitment should have a greater effect on expectations of compliance for the issue area covered by the commitment compared to unrelated issue areas.

Experimental Manipulations:

All respondents were presented with a scenario where a foreign country has, or has not, recently made a promise to pursue a particular policy. The particular country and region was not identified to avoid potential biases arising from any country- or region-specific effects among respondents. Respondents are randomly assigned to different additional facts regarding the scenario according to the following three treatments.

1) Type of Scenario (binary): The treatment group was given a military scenario, which involved a territorial dispute and the potential use of force. The control group was given an economic scenario, which involved economic problems and the potential increase of trade barriers against foreign goods.

2) Type of Commitment (trichotomous): This treatment focused on the existence and level of legalization of a commitment made by the foreign country either not to use force (military scenario), or not to raise trade barriers (economic scenario). The first treatment group was given a hard legalization prompt, where the country had signed a formal international treaty not to undertake the relevant policy option based on the type of scenario. The second treatment group was given a soft legalization prompt, where the country had participated in the creation of non-binding regional guidelines not to undertake the relevant policy option. Finally, the third treatment group was given a verbal commitment prompt, where the country simply issued a statement saying it would not pursue the relevant policy option.

3) Compliance History (binary): The treatment group was told the foreign country has a history of violating its promises. The control group was instead told the foreign country has a history of complying with its promises.

In order to also provide a baseline control group to allow better evaluations of the effects of the Type of Commitment and Compliance History treatments, an additional group is presented the general scenario for a given issue area (military/economic), but receives none of the additional prompts for the second and third treatments. The use of two binary treatments and one trichotomous treatment implies a 2x3x2 factorial design, along with an additional baseline control group for each issue area, which results in a total of 14 experimental groups.

Key Dependent Variables:

After being presented with the scenario, respondents were asked two questions regarding their beliefs about the likelihood the foreign country would subsequently comply with the relevant policy, where one question concerned military policy and the other trade policy. For each respondent the first question asked was based on the type of scenario they faced (for instance, the trade question was asked first for respondents receiving the economic scenario, followed by the military question). Response options for both questions were based on a four-point Likert scale ranging from very likely to very unlikely.

Summary of Findings:

The findings are generally consistent with expectations that legalization enhances the credibility of commitments made by foreign countries in the eyes of the U.S. public. Making commitments through more legal instruments has a much greater effect on beliefs a foreign country will subsequently follow through on its promises compared to simply issuing a verbal assurance. Furthermore, amongst legalized commitments a formal treaty yields larger gains in most instances for a country’s credibility than a softer non-binding legal arrangement.

Rather than working only in the easiest cases, international law also appears to have the most pronounced effects where the need for making credible commitments is greatest. Not surprisingly, countries with a history of violating past promises are viewed as less trustworthy, and thus less likely to abide by future commitments, than a country with a past history of compliance. Nevertheless, prior violators can improve the credibility of their future promises by making more legalized commitments, and these effects are often greater for violators than countries with a better track record of compliance. As a result, past violators may have a stronger incentive to employ international law in order to overcome deficits in their credibility compared to compliers who already have a history of fulfilling their promises. This suggests that international law can serve a screening function in separating out more serious states willing to abide by their commitments, in addition to generating ex post costs for subsequent noncompliance. While indicative from the findings of this study, further work would help to better identify and distinguish the screening function of international law compared to other mechanisms.

Contra the usual expectations that international law works best in lower stakes issue areas, the experimental findings show that the greatest gains in credibility are when making commitments in the military scenario, while more modest in situations involving international trade. However, legalized commitments appear to be limited to enhancing credibility in the specific issue at hand. The ability of international law to improve beliefs over expectations of future compliance is shown to be mainly issue-specific with fewer prospects for spillover effects into unrelated areas.

Additional Information:

By offering a specific test of the credibility mechanism, this study builds on a series of earlier surveys that found international law and legalization have a significant impact on public attitudes toward foreign policy. This study was thus intended to assess the possible role of credibility in explaining the overall effects of legalized commitments.

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