The Swiss Super League is technically not a EU league, but because of a political treaty we're treated as if we were (meaning Swiss players count as EU citizens in EU leagues) Restrictions in Switzerland - a max. of 5 non-EU players on the field for a team at any given time, with the possibility of having 2 more non-EU players on the bench.
In Italy there is no limit on the amount of non-EU players a club can have. However, each club is only allowed to buy 1 non-EU player from outside of Italy per year. In Spain and England I think the limit is 4 or 5 non-EU players per club.
England removed it's limit on the amount of non-EU's per squad. However non-EU's still need a work permit in order to play. I think France has no limit on non-EU's on a team's roster, but a match squad can have no more than 5.
Not too long ago, Chelsea fielded a team consisting of all foreigners. I think that was around 98 or 99. Probably the later. The tricky thing is with France is they let the players from their former colonies play as French.
Well, considering the only English first-teamers they had around that time were Le Saux, Wise and Duberry, that's not very hard to believe. But althought they fielded a lot of foreigners, they were still mostly EU-players. Zola/Di Matteo/Vialli-Italy, Leboeuf/Desailly-French, etc.