Both Uses

constrained
in
The Sunlight Dialogues
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A natural force, unconstrained, and not merely ignorant either; prepared for the worst—and sometimes it had come—and she had survived.†
Chpt 12 *

unconstrained = not restricted; or uninhibited

standard prefix: The prefix "un-" in unconstrained means not and reverses the meaning of constrained. This is the same pattern you see in words like unhappy, unknown, and unlucky.
There are merely unconstrained acts of holy love and hate, that is to say, of life and death, both of which are selfless, and between them ...†
Chpt 21

Definitions:

(1) (constrained)
restricted or inhibited
(2) (meaning too rare to warrant focus)
Much more rarely (and archaically), constrain can mean to force someone to do something.