The Welsh Rugby Union has blocked Shaun Edwards from taking up a coaching role at Toulon.
Initially, the WRU and head coach Warren Gatland agreed to give Edwards a chance with the three-time European champions in order to gain some coaching experience and continue his development.
However, they have recently back-tracked on sending the defence coach to France.
"Shaun will not be working with Toulon," said the WRU in a statement.
"He is a contracted employee of the WRU. Whilst we encourage coaching staff gaining experience in other environments, the scope of the opportunity at Toulon has changed and would represent an unacceptable compromise.
"Shaun remains committed to Wales up to RWC 2019."
Edwards is widely regarded as one of the best defensive coaches in the business, as he helped guide Wales to nearly five consecutive matches without conceeding a try in 2012 and the 2013 Six Nations title. Late last year, the 49-year-old signed a new four-year deal with the WRU.