In 1992, the Nevada Test Site hosted the last of over 800 underground nuclear detonations that had commenced in 1961. Five years later, in 1997, the DOE began a program of subcritical testing at the test site that has continued on through today. The philosophical differences between the two types of tests are minimal. The difference between an underground nuclear test and a subcritical experiment can be compared to the difference between firing an actual bullet as opposed to firing a blank.
You may think that the DOE isn't 'aiming' their gun at someone, and therefore no crime is committed, yet their 'gun' is in fact aimed. It is aimed at arguably the entire world. Locally, the DOE is pointing its gun at the Western Shoshone and all peoples who consume the air, the soil and water in Nevada and Utah. Critics of these tests also say that the DOE is aiming their 'gun' at any of the countries in the 'axis-of-evil,' and using these tests to send a threatening message of the U.S.'s intent to use nuclear weapons again.
Like underground nuclear tests, subcritical tests have a legacy of contamination that is stored underground. It is not impossible for the plutonium waste of subcritical tests to leach into the groundwater. The impacts to groundwater of the nearly two dozen subcritical tests conducted since 1997 have not been determined to date at the test site. Likewise, it is not impossible that subcritical tests can 'go critical' to the extent of producing some airborne fission byproducts that can eventually vent to the surface.
Since 1997, the DOE has aimed their gun and fired blanks over and over again. And the impact is no different than when a madman runs around aiming a gun at other people and firing blanks. The effect is de-stabilizing.
In early 1998, the European Parliament concluded that the United States was creating a 'crisis of confidence' in the Comprehensive Test Ban Treaty by conducting subcritical experiments and passed a resolution urging the United States to 'halt the series of subcritical tests' which could otherwise jeopardize the treaty's entry into force. The resolution mentioned that at least 15 countries expressed their concern or opposition to the tests, among them Iran.
Protests by anti-nuclear organizations, foreign governments and international bodies continued against U.S. subcritical testing through about 2003, when worldwide and local dissent began to soften for unknown reasons. Then came the North Korean government's first mention of a nuclear test on Sept. 7, 2006. That announcement came on the heels of the United States' successful completion eight days earlier of its 23rd subcritical nuclear experiment. In its Sept. 7th official reference to a planned nuclear test, North Korea's Central News Agency noted that a South Korean group, the National Alliance for the Country's Reunification, made a statement accusing the United States' subcritical test as an 'obvious criminal act of disturbing the global peace.'
Read the 1998 European Parliament resolution here: http://stopdivinestrake.com/subcritical.html