with sufficient enforcement at the point of sale, what is Obama talking about?

Simply that there ISN'T sufficient enforcement - or in some cases sufficient legal controls- at the point of sale.

I believe you're from the UK, Grishka? Over on this side of the pond in the U.S. these so-called "controls" are the province of state law, not federal/national, and in some states are worse than useless. And there's the gun show exemption Olddude has mentioned several times.