Your question points to a real tension: the Church’s “peace mandate” is universal and principled, but political actors sometimes apply international law selectively (treating it as binding only when it benefits them). Since you haven’t provided the text of a specific news article, the analysis below addresses the tension in general, using the Church’s own teaching about peace and international law.

1) What the “peace mandate” actually is in papal teaching

Across modern pontificates, peace is not treated as a slogan or mere pause in fighting; it is a moral project.

• Peace is an “enterprise of justice,” not merely the absence of war. Paul VI says peace “is not merely the absence of war,” nor “a balance of power,” nor something produced by dictatorship; rather it is “rightly and appropriately called ‘an enterprise of justice’ (Is 32.7).”1
• Peace requires the will of persons and nations, guided by justice. John Paul II teaches that it is “impossible to ensure peace for international life by looking only to the means that man can use,” because peace depends on whether people “want peace in a mature and responsible way.”2
• Peace is built day by day through a more perfect justice. John Paul II explicitly develops the idea (from Paul VI’s teaching on development) that “peace cannot be limited to a mere absence of war,” and that peace is “built up day after day” in a pursuit of an order of justice intended by God.3

So when the Church speaks of peace, it is not asking for “softness” toward wrongdoing; it asks for a just moral order in which nations act according to law and truth, not according to advantage.

• Paul VI also describes the Pope’s role as promoting principles that foster “just, rational, and peaceful relations between States,” and using good offices to settle disputes on a basis of “fraternity and honor.”4
• Pius XI grounds this in moral accountability: not only individuals, but nations must conform to God’s eternal law, with a “much greater responsibility” because national acts have broader consequences.5

2) What Catholic teaching says about international law (and why selective use is morally corrosive)

The Church links peace to rule of law at the international level—not simply to “rules,” but to rules that are genuinely universal in scope and rooted in moral value.

International law is not “whatever the strongest want”

John Paul II rejects the view that international law is just an extension of state self-interest:

Instead, international law is presented as:

• “a code of behaviour for the human family as a whole,” built from universal principles “prior to and higher than the domestic law of States.”6
• International law’s progress is tied to preserving a climate of trust and avoiding “the law of the jungle.”6

The juridical order must harmonize with the moral order

The Church’s social teaching emphasizes the hierarchy between law and morality:

• International stability requires “universal respect of the principles underlying ‘a legal structure in conformity with the moral order’.”7
• International law must avoid the “temptation to appeal to the law of force rather than to the force of law.”7
• The Church’s goal is a move from private retaliation to a real rule of law internationally, because “international law must ensure that the law of the more powerful does not prevail.”8

International law depends on moral commitments (not arbitrary advantage)

Denzinger’s compilation of magisterial teaching (drawing on Summi Pontificatus) is especially relevant to the “selective application” problem:

• If nations separate the law of nations from divine law, it is “nothing other than to pull it down from its throne… and hand it over” to advantage-seeking that denies others’ rights.9
• Holding pacts “as fluid and fleeting” and infringing “without consulting… overlooking the other party” destroys due trust and separates peoples “as by precipitous and deep chasms.”10

The Church also warns about “justice of the victors”

John Paul II highlights that the world needs not only forums and conventions, but moral courage to abide by law:

He adds a caution directly connected to selective enforcement:

• Efforts at international justice must not become “a kind of justice of the victors,” or conceal “ulterior motives of domination.”11

3) How “selective international law application” conflicts with the Church’s peace framework

Selective application usually shows up in one (or more) of these patterns:

1. Double standards: the same conduct is condemned in one case and excused in another.
2. Selective enforcement: legal obligations are invoked only when politically convenient.
3. Instrumentalizing law: legal language is used to justify advantage, rather than to secure a just common good.
4. Bypassing impartial institutions: where impartial adjudication could constrain power, it is avoided or undermined.

Catholic teaching challenges these patterns because the Church insists that international law must be:

• Valid for all without exception as a rule of law oriented to the common good.11
• Applied in justice and equity: when international laws are applied, the “inspiring principle” must be “justice and equity.”6
• Supported by coercive provisions, but oriented to justice: John Paul II hopes norms of international law will have “coercive provisions adequate to ensure their application,” precisely to avoid arbitrariness and the “law of the jungle.”6

In other words, peace is not the product of power pretending to be law. Peace requires law that genuinely binds.

4) An important nuance: the Church does not teach “pacifism at any price”

Sometimes critics of war-making point out that “peace” language is used, but then violence is still deployed. Catholic teaching therefore distinguishes:

• true peace (justice, universal moral order), from
• the rejection of every kind of force in every circumstance.

For example, the Catholic tradition allows that force can be morally justified in limited ways, especially as self-defense against aggression—while still insisting that this is ordered by justice, proportionality, and the moral law.

• John Paul II says that recourse to force for a “just cause” would be admissible only if it is “proportionate,” with due consideration for the consequences of military action.6
• A scholarly treatment of Catholic teaching notes that popes did not endorse pacifism in the simplistic sense, emphasizing readiness to repel aggressors and not confusing Christ’s “peace” with “sentimental, confused, unwise pacifism.”12

So the Church’s critique of “selective law application” is not “use no force,” but rather:

• use force (if at all) only within the morally permitted conditions, and
• do not invoke legality selectively while ignoring the same legal-moral standards when inconvenient.

5) Practical test: what would “non-selective” compliance with the Church’s peace vision look like?

If you want a concrete Catholic yardstick for whether international law is being applied faithfully (not selectively), look for:

• Consistency: the same moral-legal principles are applied to all states, not only rivals.6 11
• Moral grounding: agreements and norms are treated seriously because they connect to truth, justice, and human dignity—not “fluid and fleeting” convenience.9 10
• Impartiality: strengthening judicial mechanisms that introduce objectivity between states (e.g., support for the ICJ’s impartial role).13
• Justice-first orientation: peace is pursued through justice and universal moral order, not through domination disguised as legality.1 11
• Equity in application: applying international law according to justice and equity, not advantage.6
• Avoiding the temptation of force over law: international order is meant to prevent “law of the more powerful” from prevailing.8

Conclusion

The Pope’s peace mandate, as presented in Catholic magisterial teaching, is not merely “be peaceful.” It is: build a true peace through justice, and therefore through genuine rule of law that binds all states without exception.1 6 11 Selective application of international law—especially when it becomes “justice of the victors” or when pacts and norms are treated as disposable—directly undermines the moral and juridical harmony the Church insists is necessary for stable international life.8 10 11