What is No-Movement Clause?
A contract clause that prevents a team from trading the player without his permission.
What this tells us
When a player signs a no-movement clause, his team cannot send him to another team via trade. The player has veto power over any deal involving him. This is valuable protection for the player — it lets him control his career path and avoid unwanted relocations — but it also limits the team's flexibility if they want to rebuild or restructure their roster.
Limitations
A no-movement clause protects against trades but not against being placed on waivers or bought out (both of which can still move the player). It also doesn't prevent the team from healthy-scratching the player or reducing his ice time if they're unhappy — it only blocks outright trades. Some teams have negotiated "modified no-trade clauses" that restrict (rather than eliminate) the destinations a player can be moved to.
Example
A veteran star approaching the end of his prime might negotiate a no-movement clause as part of his contract to ensure he finishes his career with the organization he chooses, rather than being traded to a rebuilding team he didn't sign up for.