What year could NHL players join WC?

[SergeiMakarovStyle]

It must have been before 1989?

In 1989:

1989 - 15. Apr. - WHC '89 - group game - USA vs USSR
USA ): John Vanbiesbrouck (NY Rangers), Robb Stauber (New-Haven Nighthawks, AHL); John Daskalakis (Jokerit, FIN); Brian Leetch (NY Rangers ), Greg Brown (Boston College, NCAA), Jeff Norton (NY Islanders), Tom Kurvers (New Jersey Devils), Phil Housley (Buffalo Sabres), Jack O'Callahan (New Jersey Devils), Tom O'Regan (Landshut GER-1), Ed Olczyk (Toronto Maple Leafs), Randy Wood (NY Islanders), Tom Fitzgerald (NY Islanders), Paul Fenton (Los Angeles Kings), Pat Lafontaine (NY Islanders), Kelly Miller (Washington Capitals), Brian Mullen (Winnipeg Jets), Scott Young (New-Haven Nighthawks, AHL), Tom Chorske (U. of Minnesota, NCAA ), Dave Snuggerud (Buffalo Sabres), Doug Brown (New Jersey Devils), Dave Christian (Washington Capitals), Corey Millen (Ambri-Piotta, SUI ). Head coach: Tim Taylor

[stv11]

The world championships have been open to professional players since 1977.

[SergeiMakarovStyle]

Originally Posted by stv11

The world championships have been open to professional players since 1977.

Why are not all USA players from 1989 from NHL?

[Uncle Rotter]

Originally Posted by SergeiMakarovStyle

Why are not all USA players from 1989 from NHL?

A combination of some American NHLers declining to go, plus USA Hockey traditionally putting some college kids on the World team for future Olympics reference.