Last week it was revealed spying on Dotcom and an associate by the Government Communication and Security Bureau (GCSB) was unlawful.
The case around Dotcom began when the US believed he had broken copyright laws and had invoked an extradition treaty.
"Either Kim Dotcom has broken the law in the United States and he'll face trial, or he hasn't. But that's got nothing to do with whether New Zealand is a good place to make movies or not,"Mr Key told Newstalk ZB.
Mr Key said Deputy Prime Minister Bill English was not to blame after he did not tell him he'd signed a ministerial certificate to suppress actions of the GCSB from a court hearing.
The Prime Minister said he learnt of the signing while being briefed by the GCSB it had illegally spied on Mr Dotcom because it had mistaken his residency status.
Mr Key confirmed today he'd had a "30-second" conversation with the GCSB.
"I agree GCSB should have told me when I came back to New Zealand," he told Radio Live.
He said it wasn't up to Mr English to notify him.
"He would have assumed, and did assume rightfully so, that there would be a process where the ministry would tell me and they just didn't"
Mr Key apologised to Dotcom last week over the spying.