I did a quick scan of the FIA regulations and they don't appear to specify any compression ratio limits. There is a long list of what's not allowed, but compression ratio isn't mentioned.
But in the fuel specifications, that's a different matter. The fuel itself is clearly defined, and it's composition.
My interpretation is that the fuel is specified, with definite limitations. The engineers then have to make the best of what they can get out of the fuel.
And if they blow up an engine by trying a compression ratio that is too demanding, hey, that's racing.
I know that Ferrari 049 engine has 12:1 compression ratio. It is hard to have a higher ratio than that because F1 engine has a very short stroke (around 4.4 cm). Short stroke means small BDC which lead to very small TDC to reach a high compression ratio.
However, the high compression ratio (12:1) still can be reached, thanks to "valve-pocket" on the piston surface.
