Is it legal for a collections company to access my credit report?

I got a letter from a collections company saying I needed to contact them or my current credit score, XXX, might be negatively affected. Is that legal?
I understand that having a collections action filed against me will impact my credit score. But I thought that if a company looks up my credit score (like a credit card application), my credit can be negatively affected. So it seems like I might get hit twice here. . . since they quoted my credit score AND apparently have filed a collections claim.