I thought AIG provided securities. I'm sure I'm missing something obvious as it's not something I know anything about
Laws are targeted toward different types of financial institutions. Glass-Steagall was a law that applied to banks, and prevented them from selling securities.
But if a financial institution wasn't a bank, then Glass-Steagall did not apply to them. AIG did not hold deposits so it wasn't a bank. So no G-S.
Edit: to help connect the dots--what I'm referring to above are technically called "commercial banks."
https://en.wikipedia.org/wiki/Commercial_bank
From the G-S page: "The term Glass–Steagall Act usually refers to four provisions of the U.S. Banking Act of 1933 that limited commercial bank securities activities and affiliations within commercial banks and securities firms."
In general, different kinds of financial institutions are regulated by different regulatory agencies. This is as good a place to start as any: