Yes besically exactly that, we have this every year and as I understand it, yes if a team decided to sign 11 or more imports and to play them all the league probably wouldnt have a leg to stand in in EU law, however that would also bring about such a diference top to bottom in the quality in the league that it would implode, therefore the teams agree not to do it.
Its the same in my view as the wage cap, impossible to enforce in law however, even though it doesnt look like it, all teams do currently keep within wage guidelines to a degree. If they didnt the spending of a few teams (Panthers and Giants particularly) could go much higher than they do now.
However, again if they did this it would pull the league apart, so essentially both these "rules" are just that "League rules", not laws, not enforcable, but without them the league would destroy itself.