...a strategy of using or misusing law as a substitute for traditional military means to achieve military objectives. Each operation conducted by the U.S. military results in new and expanding efforts by groups and countries to use lawfare to respond to military force. 
While there is certainly legitimacy to international organizations such as the United Nations, part of the objections is that national sovereignty is the core of international relations. There was some recognition of this even in the post-WWII International Military Tribunals; the International Military Tribunal (Nuremberg) was convened by a four-power commission of the major victors, while the Japanese surrender did agree to the International Military Tribunal (Tokyo) and thus legitimized it as a national action. Admittedly, the procedure of the latter Tribunal was much less formal than that of the former, more nations were involved, there were greater language and political problems, and, in many respects, it was seen as less just than the former.
It is also seen as a form of asymmetrical warfare to counter superior military force, especially by non-national actors. American conservative legal theorists, such as Jack Goldsmith, and organizations, such as the Federalist Society, regard it with especial concern. Goldsmith, however, is a relative moderate compared to Dick Cheney and some of his advisers, such as David Addington, who based much of the George W. Bush Administration policies in dealing with terrorism on American immunity to international law. George W. Bush, for example, ruled, on February 7, 2002, wrote
"I determined.... that members of al-Qaeda, the Taliban, and associated forces are unlawful enemy combatants who are not entitled to the protections that the Third Geneva Convention provides to prisoners of war." 
U.S. concerns preceded the Bush Administration, although the term is relatively new.
International Criminal Court
Concern over the effect, if not the term, is a major reason that several major nations did not ratify the Rome Treaty for the International Criminal Court (ICC). They feared that the ICC might be used to harass rather than in the interest of justice. Goldsmith specifically called the ICC "self-defeating".
There is some sentiment, however, that a body like the ICC will be more just in applying universal jurisdiction than individual nations who have tried to extradite or prosecute individuals who neither performed the act in areas under their national jurisdictions, or against their citizens, such as Spain's extradition from Britain of Chilean president Augusto Pinochet. This is a more extensive interpretation than actions taken against foreign defendants who are variously either resident in the country taking the action (e.g., Filartiga v. Pena-Irala) or by citizens of the national actor.
Defamation of religion
Legal approaches have been used to challenge defamation of religion, especially Islam. A charge was introduced to the U.N. High Commissioner on Human Rights by the Organization of the Islamic Conference in 1999. The charge was introduced by Pakistan, entitled "Defamation of Islam",  and has been opposed by groups of often differing American ideologies, in the Coalition to Defend Free Speech.
A Saudi law firm has sent letters representing "...individuals [who] feel personally insulted, emotionally distressed and defamed by your newspaper's re-publication of..." an offensive drawing of Muhammad by a Danish newspaper.
Other applications of lawfare
Other aspects of international law are being used among nations, such as maritime law by China; this would not be under ICC jurisdiction.
Extensions to the Geneva Conventions
Additional Protocol II to the Geneva Conventions, enacted in 1977 but not ratified by many major nations, is another area in which major nations have concerns that it may be adapted to lawfare. Previously, Common Article 3, and the Third Geneva Convention and Fourth Geneva Convention applied to wars between nation states. "This Article proved to be inadequate in view of the fact that about 80% of the victims of armed conflicts since 1945 have been victims of non-international conflicts and that non-international conflicts are often fought with more cruelty than international conflicts." In an attempt to protect civilian populations and combatants in conflicts involving non-national actors, the Protocol extended the Conventions' coverage to such conflicts. The major concern was that it might legitimize the non-national actors into at least quasi-states. 
Without judging the appropriateness of the actions of the George W. Bush Administration, the Additional Protocol would have clarified, to at least some extent, the status of al-Qaeda prisoners. The Administration, without accepting Protocol II, eventually allowed secret visits to prisoners in extrajudicial detention by the International Committee of the Red Cross.
- Lawfare, the Latest in Asymmetries, Council on Foreign Relations, 18 March 2003
- Aziz Huq (22 November 2006), Waging Lawfare: Commentary, Brennan Center for Justice, New York University
- George W. Bush (July 20, 2007), Interpretation of the Geneva Conventions Common Article 3 as Applied to a Program of Detention and Interrogation Operated by the Central Intelligence Agency, Executive Order 13440
- Jack Goldsmith (2003), "The Self-Defeating International Criminal Court", University of Chicago Law Review
- Coalition to Defend Free Speech
- Christopher Hitchens (March 2, 2009), "Don't Say a Word: A U.N. resolution seeks to criminalize opinions that differ with the Islamic faith.", Slate
- Christopher Hitchens (8 March 2010), "Yamani or Your Life: A nasty attempt to coerce Danish newspapers into apologizing for the cartoons of Mohammed.", Slate
- James Kraska and Brian Wilson (11 March 2009), "China wages maritime "lawfare"", Foreign Policy
- Diplomatic Conference on the Reaffirmation and Development of International Humanitarian Law applicable in Armed Conflicts (8 June 1977), Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts (Protocol II), International Committee of the Red Cross