Technically, this is true. The nomination is decided by delegates to this summer's convention, not directly by voters. But it's probably not a terribly helpful argument to make at a time when Republican establishment types are openly talking about wresting the GOP nomination from Donald Trump at the convention. Trump has said doing so could lead to "riots."
And the RNC said in a statement to The Washington Post that those delegates must represent the voters.
"Every RNC member is entitled to have their own interpretation of the rules," RNC spokeswoman Allison Moore said. "However, the rules clearly require states to bind their delegates based off of the state’s preference vote."
It's important to note in all of this that the rules governing the convention itself are subject to change: A 112-member convention rules committee will convene at the start of the event and will be able to revise and set at least some of its own rules. Its members — one man and one woman from each state and territory — are elected by their peers. North Dakota's will not be elected until after the state convention in April.