My old friend Jennifer Boettcher decided to investigate this question, since:
According to the Office of Management and Budget (OMB), all federal offices must use NAICS for federal statistical reporting purposes. Continued use of SIC for nonstatistical purposes is usually left to the discretion of the agency. Some statutes may refer to SIC -- these are being addressed. For example, the HSR Premerger Notification Rules mentioned SIC, but that was easily remedied by using notices in the Federal Register, such as the one allowing the change from SIC to NAICS in 2001.
Unfortunately, when she contacted the Securities and Exchange Commission (SEC) about why she never got a satisfactory answer: "We will take that under advisement".
The division responsible for choosing which industrial classification system
to use is the Division of Corporation Finance. She spoke with a staff member at the Division about why the SEC has not converted. The main reason given was that it would require too much work for the Office of Information Technology to change. He said there were no immediate plans to covert from SIC to NAICS. When I asked about the new IDEA software to replace EDGAR, he said IDEA is still in the concept phase. She asked him to put NAICS into the concept.
When other federal government agencies converted to NAICS:
Census Bureau: started in 1997 and completed in 2002
IRS: 1998 (in 2003, 95.9% of Partnership tax receipts used NAICS. Proving companies and accountants have adopted NAICS)
SSA: 1999 (employer establishments to assign establishment’s activities)
SBA: 1999 (SBA assigns small business size standards to NAICS codes)
FTC: 2001 (looking at anti-trust premerger issues)
BEA: 2003 (looking at the National Income and Product Accounts)
BLS: 2004 (labor, wages, PPI, etc are measured using NAICS)
EPA: 2006 (connecting Toxic Release Index to NAICS)
Learn more about NAICS
Sorry for the delay in reporting back.