I took a look at the UN convention [1]. Article I states:
1. Each State Party to this Convention undertakes not to engage in military or any other hostile use of environmental modification techniques having widespread, long-lasting or severe effects as the means of destruction, damage or injury to any other State Party.
2. Each State Party to this Convention undertakes not to assist, encourage or induce any State, group of States or international organization to engage in activities contrary to the provisions of paragraph 1 of this article.
Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques - Article I
[Bold face is my emphasis]
The remaining articles are all procedural except for article II which defines what is meant by weather modification:
As used in article 1, the term "environmental modification techniques" refers to any technique for changing - through the deliberate manipulation of natural processes - the dynamics, composition or structure of the Earth, including its biota, lithosphere, hydrosphere and atmosphere, or of outer space.
Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques - Article II
What this means is that one may modify weather if the effects are localized, short term and not severe or if the modification is for civilian purposes. The prohibition is on
use and not on research.
The US Air Force document [2] discusses the UN Convention and legality. They explain the scope of their study as follows:
In conducting the research for this study, the broadest possible interpretation of weather-modification was initially embraced, so that the widest range of opportunities available for our military in 2025 were thoughtfully considered. However, for several reasons described below, this paper focuses primarily on localized and short-term forms of weather-modification and how these could be incorporated into war-fighting capability. The primary areas discussed include generation and dissipation of precipitation, clouds, and fog; modification of localized storm systems; and the use of the ionosphere and near space for space control and communications dominance. These applications are consistent with CJCSI 3810.01, “Meteorological and Oceanographic Operations.” [11]
Weather as a Force Multiplier: Owning the Weather in 2025
Chapter 2, p. 6 (p. 14 of 52).
Footnote 11 explains what CJCSI 3801.01 is:
CJCSI 3810.01, Meteorological and Oceanographic Operations, 10 January 95. This CJCS Instruction establishes policy and assigns responsibilities for conducting meteorological and oceanographic operations. It also defines the terms widespread, long-lasting, and severe, in order to identify those activities that US forces are prohibited from conducting under the terms of the UN Environmental Modification Convention. Widespread is defined as encompassing an area on the scale of several hundred km; long-lasting means lasting for a period of months, or approximately a season; and severe involves serious or significant disruption or harm to human life, natural and economic resources, or other assets.
Weather as a Force Multiplier: Owning the Weather in 2025
Footnotes to Chapter 2, p.7 (p.15 of 52)
What this means is that they are aware of their treaty obligations and were
speculating about the potential military applications of technology that might feasibly be available in 2025 as envisaged in 1996. What I read there explains the purpose of some ionospheric experiments people were complaining about 15 or so years ago. On the grounds that large scale weather modification was deemed to be unfeasible they reduced their scope to what they believed to be legal under the convention anyway.
It's interesting to note that the convention applies to operations against State Parties. The scenario they described in Chapter 1 involved a drugs cartel who are not State Parties, so from a legalistic point of view it is not obvious that the "widespread", "long-lasting", or "severe" restrictions would apply.
While I can well imagine that there are questions of interpretation of the words "widespread", "long-lasting", and "severe", they haven't been tested in a court and the interpretation in the CSCJI 3810.01 is certainly going to have been written by a senior lawyer, so this does not constitute evidence that they are
deliberately planning to violate the weather-modification treaty. I wouldn't exactly say that there's nothing to see here, but it's within the arena of democratic debate and cannot be seen as a conspiracy.
[1] http://www.un-documents.net/enmod.htm
[2] https://www.geoengineeringwatch.org/documents/vol3ch15.pdf
The Chaper X page m (page n of N) notation is because the internal numbering of the document has the introductory material numbered with roman numerals with the pages numbered using Western Arabic numerals beginning at 1 after the introductory material, as is customarily practiced. The pdf numbering is in square brackets and is just a "physical" page count.