Copyright statute in USA
In copyright statute, it said, if you made a copy costed over $1,000 within 180 days, you would breach the law.
The above provision is just related with audivideo work(e.g. movie).
By the way, the 180 days is not fixed. It may be any 180 days but interruped.
In a simple, you download movie not over $1000 of value and should be OK.
How to decide $ 1,000? Refer to the market price generally.