리라는

'The assumption that it will…'

-리라는 turns a confident expectation into something a noun can carry — a belief, a hope, a rule: 잘되리라는 확신이 없었음 'he had no conviction that it would go well.' Several lines here use the fixed frame 리라는 법은 없다 'there's no rule saying it will', a polite way to knock down an assumption: 등산하지 못하리라는 법은 없죠 'there's no law saying you can't hike.' It sounds a touch literary. (모지리라는 말 in one line is a different word entirely.)

Register: formal, considered speech