What's borderline legal?
I have watched a video and one of them said, 'I have done a lot of borderline legal things when I was in university'
I am not sure what I have heard, 'borderline and legal things' 'borderline legal things'?
I also read 'borderline illegal things' on Google. Again, what is it and how do you use these phrases?

Question

What's borderline legal?
I have watched a video and one of them said, 'I have done a lot of borderline legal things when I was in university'
I am not sure what I have heard, 'borderline and legal things' 'borderline legal things'? 
I also read 'borderline illegal things' on Google. Again, what is it and how do you use these phrases?

Answer

On the edge of being legal/illegal (i.e. subject to interpretation)