This quote from this Montreal Gazette article says it well:
"At issue, according to the NHLPA, is that the players’ union is not a group certified by the Quebec Labour Board. The NHLPA adds that, under Quebec law, an employer – the Canadiens, in this case – cannot lock out employees – Habs players, in this case – unless they are represented by a union certified by the QLB."
The Ontario government has paved the way in favour of the owners already, so Toronto and Ottawa won't be so lucky. It is also said that the Alberta board has received filings from the NHLPA already. Talks are in progress with BC and Manitoba.