This is as basic as it gets for mineral regulations. A full (bankable) feasibility study is required to claim reserves.
There is absolutely no shortage of SEC comment letters and published decisions about this. They should be incredibly easy to find. Some examples:
"Revise throughout to clarify that under Industry Guide 7 companies cannot enter the development stage or production stage until they have defined a proven or probable reserve with a bankable feasibility study."
"As you do not have a proven or probable reserve established by a final bankable feasibility study, please remove all economic indicators including production tons per day, production capacities, estimated mine life, and mineral recoveries. All of these economic indicators assume the existence of a reserve."
"We expect that you would need to adhere to the following guidance in the course of preparing a reserve report for any of your properties.
• Competent professional engineers conduct a detailed engineering and economic study, and the “bankable” or “final” feasibility study demonstrates that a mineral deposit can be mined profitably at a commercial rate.
•The historic three-year average commodity price is used in any cash flow analysis that is used to designate reserves
• You are able to demonstrate that you will receive any required permits not yet obtained, and that the primary environmental document has been filed with the appropriate governmental authorities.
Please revise your disclosure throughout this document to ensure you do not prematurely indicate mining operations on mining properties will occur before a proper feasibility study and economic viability determination has been conducted."
"We expect you would need to conduct or obtain a final feasibility study before designating such estimates as reserves, based on the definitions in Industry Guide 7, where a comprehensive evaluation (e.g. considering market prices, unit costs, recoverability, and other material factors) concludes legal and economic feasibility.
This is the most basic of mineral reporting rules. No reserves until a positive bankable feasibility study prepared by qualified and independent experts is completed.
If you can't find these or the many other statements which prove it, give WFW a call. As professionals, they can point you right to this basic information. For a hefty fee, of course. Because that is their job.