Can you post celebrity pictures on your blog?

[Pudding Cup]

If I was doing a blog on a celebrity, in my case, a MMA fighter - can I save pictures from their twitter/facebook account and showcase it on my blog as long as I don't claim rights or ownership to the picture?

Or would I need to contact them to get permission before posting?

I want to be respectful and stay within legal boundaries when I write. I'd rather be safe and not use the pictures and have just text, than disrespectfully steal someone one else's pictures.

I already use creative commons for my general photo finding, but when writing about a specific person it's not as easy to find pictures.

Any info on this would be great. Thanks.