They are allowed to. However, part of the adoption process is proving you are capable of supporting a child. If they can't pass, and most mentally disabled people would not be able to, then they don't get the child. It isn't like buying a puppy.
FP
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LiveWire's resident furry.
I am the God of Unsultry Pleasures. Bow to me!
I'm a Level 21 Disco Bandit!
Malo periculosam libertatem quam quietum servitium.