It can be understood from the passage that the quotas imposed in the past by national leagues ----.

Not long ago, football was not a good example of
globalization. The labour market in international club
football was highly protected. National leagues like
Italy's Serie A and Spain's La Liga imposed quotas
on their teams, allowing them to import only a limited
number of players. Some teams could have only two
foreign players on the field. This arrangement,
however, began to crumble in 1995, when the
European court ruled that the difference of treatment
of nationals from other EU countries was anticonstitutional.
This permitted players to move freely
within the EU, and made the club teams much more
multi-national. Now it is not unusual for a majority of
the players on a successful league team to be
foreign nationals.