I'm posting this as an official answer, but it's unfair of me to do so. You already knew about this (or could have easily chased it down yourself) and I can't find or imagine anything more. I'm impressed this exists. I had no idea weather modification using any method was effective enough to require this much regulation.
Public Law 92-205, 15 USC § 330
No person may engage, or attempt to engage, in any weather modification activity in the United States unless he submits to the Secretary such reports with respect thereto, in such form and containing such information, as the Secretary may by rule prescribe. The Secretary may require that such reports be submitted to him before, during, and after any such activity or attempt. (Pub. L. 92–205, § 2, Dec. 18, 1971, 85 Stat. 736.)
and from NOAA:
P.L. 92-205, enacted December 18, 1971 (amended by Public Law 94-490, Section 6(b), October 15, 1976) requires that all non-federal weather modification activities in the United States and its territories be reported to the Secretary of Commerce. The National Oceanic and Atmospheric Administration has implemented the Act and the current reporting requirements are published in the Code of Federal Regulations (15 CFR 908).
Respondents to this data collection are operators of aircraft which engage in cloud-seeding and other related activities in an attempt to modify the weather, i.e., to increase precipitation, mitigate hail, and disperse fog. They are required to file two one-page reports annually. Each project
must file with NOAA an initial report (Form 17-4) and a final report (Form 17-4A) - or an interim report on the same form if the project continues beyond December 31.
Beginning in 2000, the NOAA Forms 17-4 and 17-4A became available on the Internet at http://www.corporateservices.noaa.gov/~noaaforms/eforms/
in order for the respondents to have the capability of being able to fill out and print forms on-line. However, the forms can not be submitted electronically at this time because the forms are required to be signed by the equipment operator. The forms may be faxed to (301) 713-1459 to the attention of Karen Williams or may be mailed to the NOAA - Weather Modification Reporting Office in Silver Spring, MD. Electronic signature capability is being planned but security requirements are still to be addressed. The NOAA Forms 17-4 and 17-4A are still available by mail to those who do not have access to a computer.
Regrettably, the link is no longer active. However, the funniest part of this comes from the following statement in that report:
Note: currently a redesign of the forms is planned, as the previously fillable forms were locked by a retired employee.
Honestly! They're going to spend a ton of money redesigning forms because no one is bright enough to type "remove acrobat passwords" into Google and get any one of the bazzillions of PDF file password removal tools and just unlock the file. I've done this myself... it takes seconds. I wonder how many of my tax dollars were spent on that endeavor?